Use the flex-grow Property to Expand Items

Tell us what’s happening:

Why this code, doesn’t show “#box-1” or “#box-2” till we use the “flex-grow” property ?

Your code so far

  #box-container {
    display: flex;
    height: 500px;
  #box-1 {
    background-color: dodgerblue;
    height: 200px;
    flex-grow: 1;
  #box-2 {
    background-color: orangered;
    height: 200px;
    flex-grow: 3;

<div id="box-container">
  <div id="box-1"></div>
  <div id="box-2"></div>

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.87 Safari/537.36.

Link to the challenge:

Because the parent object is defined with display equal to flex. If you changed it to block it would show the boxes. But they would not flex…