JSFiddle - React, Tailwind, and code Playground

HTML

<div class="vertically-center">
  <div>
    <div style="border: 1px solid black;">some text</div>
  </div>
</div>

CSS

.vertically-center
{
  display: table;

  width: 100%;  /* optional */
  height: 100%; /* optional */
}

.vertically-center > div
{
  display: table-cell;
  vertical-align: middle;
}


html, body
{
  height: 100%;
}

body
{
  margin: 0;
  box-sizing: border-box;
}