JSFiddle - React, Tailwind, and code Playground

HTML

<div id='wrap'>
  <div id='posts'>
    <br />
    <br />
    <br />
    <br />
  </div>

  <div id='sidebar'>
    <br />
    <div class='widget'></div>
    <div class='widget'></div>
  </div>
</div>

CSS

#wrap {width: 100%;display: table;}
#wrap > div { margin: 0; width: 100%; }
#wrap #sidebar { 
            display: table-cell; 
            width: 25%;
            background: teal;
            min-height: 100%;
        }
        #wrap #posts { 
            display: table-cell; 
            width: 75%;
            background: orange;
            min-height: 100%;
        }