JSFiddle - React, Tailwind, and code Playground

HTML

<div class="outer-container">
    <span class="txt-vertical-align">Hello World</span>
</div>

CSS

.outer-container {
    background-color: green;
    color: #fff;
    width:400px;
    height:400px;
}

.outer-container {
   display: table;
   width: 100%;
}
.txt-vertical-align {
   display: table-cell;
   text-align: center;
   vertical-align: middle;
}