JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div>
    <b>List 1:</b><br />
    <ul>
      <li>Item 1a</li>
      <li>Item 1b</li>
    </ul>
  </div>
  <div class="rightx">
    <b>List 2:</b><br />
    <ul>
      <li>Item 2a</li>
      <li>Item 2b</li>
    </ul>
  </div>
</div>

CSS

.container {
  display: grid;
  grid-template-columns: auto auto;
}

.container > div {
  border: 2px solid blue;
}