JSFiddle - React, Tailwind, and code Playground

HTML

<div id="parentDiv">
<div class="childDiv"></div>
</div>

CSS

#parentDiv
{
  display: flex;
  justify-content: flex-end;
  flex-direction: column;
  width:300px;
  height:300px;
  background-color:#ccc;
  background-repeat:repeat
}
#parentDiv .childDiv
{
  height:100px;
  width:30px;
  background-color:#999;
}