JSFiddle - React, Tailwind, and code Playground

HTML

<div class="div1">1</div>
<div class="div2">2</div>
<div class="fix">3</div>

CSS

.div1{
    width:50px;
    height:500px;
    background:yellow;
    float:left;
}
.div2{
    width:50px;
    height:500px;
    background:red;
    float:right;
}
.fix{
    overflow:hidden;
    *zoom:1;
    background:green;
    height:500px;
}