JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div class="container">
      <div class="first">
          <div class="innerFirst">Blablub</div>
      </div>
      <div class="second">
          <div class="innerSecond">When the container is smaller than 169px, than the yellow div pops below the red div</div>
      </div>
    </div>
</body>

CSS

.container{
    width:168px; 
    padding: 5px;
    display: table;
    background-color:green; 
}

.first{
    display: table-cell;
    overflow: hidden;
    width: 15%;
    height: 100%;
    background-color: red;
}

.second{
    display: table-cell;
    overflow: hidden;
    width: 70%;
    height: 100%;    
    background-color: yellow;    
}

.innerFirst{
    
    height: 100%; 
    width:100%; 
    vertical-align: middle;
}

.innerSecond{
    
    height: 100%; 
    width:100%; 
    vertical-align: middle; 
    text-align: center
}