JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
 <div class="divOne"></div>
 <div class="divTwo"></div>
</div>

CSS

.container {
  width: 100%;
}

.divOne {
  width:50%;
  height: 100px;
  background-color: yellow;
  float: left;
}

.divTwo {
  width:50%;
  height: 100px;
  background-color: blue;
  float: left;
}
@media screen and (max-width:600px) {
  .divOne, .divTwo {
    width:100%;
  }
}