JSFiddle - React, Tailwind, and code Playground

HTML

<div class="one">div1</div>
<div class="two">div2</div>
<div class="three">div3</div>

CSS

.one,.two,.three{
    border: 1px solid;
    float: left;
    margin: 5px;
    width: 25%;
    text-align: center;
    padding: 15px;
}

@media (max-width: 519px) {	
    .one,.two,.three{
        border: 1px solid red;
        width: 100%;
    }
}