JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
    <div class="left">
        <span>
            <em>
                Blah left
            </em>    
        </span>
    </div>
    <div class="right">
        <span>
            <em>
                Blah right
            </em>
        </span>
    </div>
</div>

CSS

html, body {
    height: 100%;
    width: 100%;
    font-size: 13px;
}

.parent {
    height: 50px;
    background-color: grey;
    font-size: 1.6em;
}

.left {
    margin-left: 2%;
    float: left;
    background-color: yellow;
    height:100%;   
}

.right {
    margin-right: 2%;
    float: right;
    background-color: red;
    height:100%;    
}
.parent span{
    display:table;
    height:100%;
}
.parent em{
    display:table-cell;
    vertical-align:middle;
    
}