title: Flexbox div doesn't take the whole width
body: <p>I'm trying to understand how <code>display:flex</code> works, but whenever I set it, the childs don't take the whole width. I was expecting the three divs getting a 33% of the screen width. What am I doing wrong?</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.flexbox {
    display: flex;
  }
  
  .flexbox div {
    border: 1px solid black;
    padding: 10px;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="flexbox"&gt;
    &lt;div&gt;One&lt;/div&gt;
    &lt;div&gt;Two&lt;/div&gt;
    &lt;div&gt;Three&lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>