title: set a div's min height depending on a height of another div
body: <pre><code>&lt;div id="container"&gt;
    &lt;div id="div1"&gt;
    &lt;/div&gt;
    &lt;div id="div2"&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>.given the example above, how do I set the height of div2 as the minimum height of div1? also vice versa by using only css. TIA!</p>