JSFiddle - React, Tailwind, and code Playground

HTML

<div class="contenedor">
    <div id="contenido">&nbsp;</div>
</div>

CSS

.contenedor {
  display: flex;
  flex-direction: column;
  justify-content: center;
  background-color:#666;
  height:500px;
}

#contenido{
    height:150px;
    width:150px;
    background-color:#000;
    margin:0 auto;    
}