Make column elements equal height on each row

Question

This is the layout I want to get:

So regardless of what's contained in these divs, I want all of them to stretch to the height of the largest div on that row so that everything remains alligned.

However, I cannot think of a way that I can make the items have the same height so that they are all aligned. I could use CSS tables (using display: table), but then I'd need to split it up by rows, as opposed to columns, so the semantics would get messed up.

Other than display: table, I feel like there should be a way with flexbox, but I can't for the life of me figure out what it could be. I can make the container div the same with flex by adding another container around the columns, but I'm not sure how I'd use that to make the children have the same height.

I could also use Javascript to loop through all of them, but that fees like a horrible, inefficient solution.

Here's some code which shows A) What I want to have, regardless of the content inside the divs, and B) what currently happens.

Codepen

* {
  font-family: Helvetica, sans-serif;
}

h2 {
  text-align: center;
  clear: both;
  padding-top: 2em;
}

.col {
  float: left;
  width: 30%;
  background-color: #ebebeb;
  margin-left: 1em;
}
.col div {
  padding: 1em;
  width: 80%;
  margin: 0 auto;
}
.col .sectionOne {
  background-color: #2b2b2b;
  color: #fff;
}
.col .sectionTwo {
  background-color: #5f5f5f;
  color: #fff;
  margin-top: 1em;
}
.col .sectionThree {
  background-color: #8c8c8c;
  color: #fff;
  margin-top: 1em;
}

<h2>Everything Aligned. The world is a happy place.</h2>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>


<h2>Misaligned. Chaos descends.</h2>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus
    et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Adipiscing elit.Lorem ipsum
    dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>

EDIT: Each .col represents a post in the Wordpress archive page, so it must be arranged in columns.

Answer 1

Here's a simple solution using CSS Grid Layout.

Features:

• all rows are the height of the tallest element in the row
• the elements flow in columns, not rows
• extra HTML containers can be removed
• the code is simple and efficient

codepen

body {
  display: grid;
  grid-template-rows: repeat(3, auto);
  grid-auto-columns: 1fr;
  grid-auto-flow: column;
  grid-gap: 1em;
  padding: 1em;
}

.sectionOne   { background-color: #2b2b2b; }
.sectionTwo   { background-color: #5f5f5f; }
.sectionThree { background-color: #8c8c8c; }
div           { padding: 1em; color: #fff; }

<div class="sectionOne">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.
</div>
<div class="sectionTwo">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
</div>
<div class="sectionThree">
  Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
</div>
<div class="sectionOne">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit.
</div>
<div class="sectionTwo">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
</div>
<div class="sectionThree">
  Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
</div>
<div class="sectionOne">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.
</div>
<div class="sectionTwo">
  Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
</div>
<div class="sectionThree">
  Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
</div>

Browser Support for CSS Grid

• Chrome - full support as of March 8, 2017 (version 57)
• Firefox - full support as of March 6, 2017 (version 52)
• Safari - full support as of March 26, 2017 (version 10.1)
• Edge - full support as of October 16, 2017 (version 16)
• IE11 - no support for current spec; supports obsolete version

Here's the complete picture: http://caniuse.com/#search=grid

Answer 2

The only way to do that with Flexbox, if not to use script, is to remove the col and use the order property to visually position them column wise.

The reason is simple, the sections need to be siblings to enable equal height per row.

Based on how many items it will be, one might need to group them to keep the necessary CSS rules on a reasonable level, though as that is not available in the question, I here show a solution based on the existing amount of items.

As a replacement for the removed col's background color, I used a border to make it simple, but one can i.e. use pseudo elements or an extra inner element to accomplish the same effect.

Updated codepen

Stack snippet

* {
  font-family: Helvetica, sans-serif;
}

.cols {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -ms-flex-wrap: wrap;
      flex-wrap: wrap;
  -ms-flex-pack: distribute;
      justify-content: space-around;
}
.cols div {
  padding: 1em;
  border: 1em solid #ebebeb;
  box-sizing: border-box;
  width: 30%;
}
.cols .sectionOne {
  background-color: #2b2b2b;
  color: #fff;
  -webkit-box-ordinal-group: 2;
      -ms-flex-order: 1;
          order: 1;
}
.cols .sectionTwo {
  background-color: #5f5f5f;
  color: #fff;
  border-width: 0 1em 1em 1em;
  -webkit-box-ordinal-group: 3;
      -ms-flex-order: 2;
          order: 2;
}
.cols .sectionThree {
  background-color: #8c8c8c;
  color: #fff;
  border-width: 0 1em 1em 1em;
  -webkit-box-ordinal-group: 4;
      -ms-flex-order: 3;
          order: 3;
}

<div class="cols">

  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus
    et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>


  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>


  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Adipiscing elit.Lorem ipsum
    dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>

</div>

---

Updated

As mentioned, and as a sample for more than 3 posts, and a 3 column layout, one can simply repeat the above solution, with an extra rule giving all but the first cols a top margin.

Stack snippet

* {
  font-family: Helvetica, sans-serif;
}

.cols {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -ms-flex-wrap: wrap;
      flex-wrap: wrap;
  -ms-flex-pack: distribute;
      justify-content: space-around;
}
.cols + .cols {
  margin-top: 1em;
}
.cols div {
  padding: 1em;
  border: 1em solid #ebebeb;
  box-sizing: border-box;
  width: 30%;
}
.cols .sectionOne {
  background-color: #2b2b2b;
  color: #fff;
  -webkit-box-ordinal-group: 2;
      -ms-flex-order: 1;
          order: 1;
}
.cols .sectionTwo {
  background-color: #5f5f5f;
  color: #fff;
  border-width: 0 1em 1em 1em;
  -webkit-box-ordinal-group: 3;
      -ms-flex-order: 2;
          order: 2;
}
.cols .sectionThree {
  background-color: #8c8c8c;
  color: #fff;
  border-width: 0 1em 1em 1em;
  -webkit-box-ordinal-group: 4;
      -ms-flex-order: 3;
          order: 3;
}

<div class="cols">

  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus
    et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>


  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>


  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Adipiscing elit.Lorem ipsum
    dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>

</div>

<div class="cols">

  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>


  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa.
  </div>


  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus.
  </div>

</div>

Answer 3

In the futur , you may use grid and a single container:

* {
  font-family: Helvetica, sans-serif;
}

h2 {
  text-align: center;
  clear: both;
  padding-top: 2em;
}

.grid {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  grid-gap: 1em;
  background: repeating-linear-gradient(to right, transparent 1%, #ebebeb 1%, #ebebeb 33%, transparent 33%, transparent 34%);
}

div {
  padding: 1em;
}

div div {
  margin: 0 4%;
}

.sectionOne {
  background-color: #2b2b2b;
  color: #fff;
  grid-row: 1
}

.sectionTwo {
  background-color: #5f5f5f;
  color: #fff;
  grid-row: 2
}

.sectionThree {
  background-color: #8c8c8c;
  color: #fff;
}

.grid {counter-reset:div}
.grid>div:before {
  counter-increment:div;
  content:'div number:'counter(div);
  background:yellow;
  color:red;
  padding:0 0.5em;
  font-size:0.75em;
}

<h2>Everything Aligned. The world is a happy place.</h2>
<div class="grid">
<!-- first post-->
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur
    in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
<!-- end first post-->
<!-- second post-->
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, <br/>consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
<!-- end second post-->
<!-- third post-->
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus lorem
  </div>
<!-- end third post-->
</div>

usefull ressource :

• https://css-tricks.com/snippets/css/complete-guide-grid/

• http://gridbyexample.com/

• and the codepen to play with

• Are you arrived in the future yet ? check it out here http://caniuse.com/#search=grid ;)

Answer 4

If you organize them in rows instead of columns, you can use display: flexon the (row) containers, which has the effect you want. Note: I also used fixed (percentage) width settings on the child elements to achieve this.

.col {
  display: flex;
  margin-bottom: 10px;
}

.col>div {
  width: 31%;
  margin: 1%;
  background: #ddd;
}

<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus
    et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Adipiscing elit.Lorem ipsum
    dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>

Answer 5

This can be accomplished with flexbox, though note that it isn't fully supported in Internet Explorer 11.

First, replace your float: left on .col with display: flex.
Second, move your margin-top: 1em declarations to .col.

* {
  font-family: Helvetica, sans-serif;
}

h2 {
  text-align: center;
  clear: both;
  padding-top: 2em;
}

.col {
  display: flex;
  margin-top: 1em;
  background-color: #ebebeb;
}
.col div {
  padding: 1em;
  width: 80%;
  margin: 0 auto;
}
.col .sectionOne {
  background-color: #2b2b2b;
  color: #fff;
}
.col .sectionTwo {
  background-color: #5f5f5f;
  color: #fff;
}
.col .sectionThree {
  background-color: #8c8c8c;
  color: #fff;
}

<h2>Everything Aligned. The world is a happy place.</h2>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>


<h2>Misaligned. Chaos descends.</h2>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus
    et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>
<div class="col">
  <div class="sectionOne">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Adipiscing elit.Lorem ipsum
    dolor sit amet, consectetur adipiscing elit.
  </div>
  <div class="sectionTwo">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum quis sem interdum, aliquam magna non, vestibulum nibh. Curabitur in eros ornare, ultricies tellus et, venenatis dolor. Curabitur in eros ornare, ultricies tellus et, venenatis dolor.
  </div>
  <div class="sectionThree">
    Cras eget lectus non dolor congue dapibus in id massa. Nullam porta est accumsan lacinia tempus. Curabitur convallis ex nec vestibulum semper. Vivamus lorem
  </div>
</div>

Note that flexbox doesn't have collapsing margins or anything like border-spacing for tables. This can be resolved by setting margin on .col div, though you may want to change the background.

Also, your use of the name .col is counter-intuitive, as you actually have three sections per row. You might want to watch out for that!

Hope this helps! :)