JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<div class="container">
  <h1 class="header">header</h1>
  <div class="row">
    <div class="colDiv col-sm-6 col-md-4 col-lg-3">
      <p>ColumnA</p>
    </div>
    <div class="colDiv col-sm-6 col-md-8 col-lg-9">
      <p>ColumnB</p>
    </div>
  </div>
</div>

CSS

@media (max-width: 768px) {
  .header{font-size:20px};
}
@media (min-width: 769px) and (max-width: 991px) {
  .header{font-size:30px};  
}
@media (min-width: 992px) and (max-width: 1199px) {
  .header{font-size:40px};  
}
@media (min-width: 1200px) {
  .header{font-size:50px};  
}

.header{
  text-align:center;
}
.colDiv{
  border:solid 1px #33aaff;
}