JSFiddle - React, Tailwind, and code Playground

HTML

<div class="grid">
    <div style="grid-column:span 1 / 1; grid-row:1;">track before the explicit grid</div>
    <div style="background:cyan; grid-column:1; grid-row:1;">track in the explicit grid</div>
    <div style="grid-column:2; grid-row:1;">track after the explicit grid</div>
</div>

CSS

.grid {
        display:grid;
        grid-template-columns: 200px;
        grid-template-rows: 100px;
        grid-auto-columns: 300px 50px;
    }

    .grid > * {
        border:solid;
    }