   grid-gap: 10px;
    border: 10px;
    border-style: solid;
  }
  item {
    background-color: grey;
    height: 250px;
    width: 250px;
  }
</style>
</head>
<body>
  <grid>
    <item>1</item>
    <item>2</item>
  </grid>
</body>
<script>
    /* Force a relayout */
    document.body.offsetHeight;
    document.querySelector("item").style["height"] = "125px";
</script>
</html>