JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
  <div>
    grid item<br> minimum width = 200px<br> maximum width = 400px
  </div>
  <div>
    grid item<br> minimum width = 75%<br> maximum width = 1fr
  </div>
</div>

CSS

#container {
  display: grid;
  grid-template-columns: minmax(200px, 400px) minmax(75%, 1fr);
  grid-gap: 10px;
  height: 100px;
  border: 1px solid gray;
}

#container > div {
  background-color: lightgreen;
  padding: 5px;
}