Is it possible to mix rows and columns with flexbox?
<p>In other words, is it possible to achieve this?</p>

<p><a href="https://i.stack.imgur.com/gp9cV.png" rel="noreferrer"><img src="https://i.stack.imgur.com/gp9cV.png" alt="enter image description here"></a></p>

<p><em>Note:</em> This is the best I could get:</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>html, body, .container {
  height: 100%;
}

.container {
  border: 1px solid green;
  display: flex;
  flex-wrap: wrap;
}

.container &gt; div {
  border: 1px solid black;
  background: #ececec;
  flex: 1;
}

.container &gt; div:nth-of-type(1) {
  flex: 1 1 100%;
}

.container&gt;div:nth-of-type(4) {
  flex: 1 1 100%;
}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="container"&gt;
  &lt;div&gt;Div 1&lt;/div&gt;
  &lt;div&gt;Div 2&lt;/div&gt;
  &lt;div&gt;Div 3&lt;/div&gt;
  &lt;div&gt;Div 4&lt;/div&gt;
&lt;/div&gt;</code></pre>
</div>
</div>
</p>

<p><a href="http://jsfiddle.net/kzbbb/249/" rel="noreferrer">http://jsfiddle.net/kzbbb/249/</a></p>