HTML

<div class="scale"></div>

CSS

.scale {
    width: 100px;
    height: 100px;
    background: teal;
    transform: scale(0.5, 1.3);
}

This example will scale the div to 100px * 0.5 = 50px on the X axis and to 100px * 1.3 = 130px on the Y axis.

The center of the transform is in the center of the div, 50% from left and 50% from top.