Pixel is a static measurement, while percent and EM are relative measurements. The size of an EM or percent depends on its parent. If the text size of body is 16 pixels, then 150% or 1.5 EM will be 24 pixels (1.5 * 16). Look at CSS Units for more measurement units.
CSS
Transition + Transformation
This example does not work in Internet Explorer 9 and earlier versions.
Hover over the div element above, to see the transition effect.
<style> div { width: 100px; height: 100px; background: red; -webkit-transition: width 2s, height 2s, -webkit-transform 2s; /* Safari */ transition: width 2s, height 2s, transform 2s; } div:hover { width: 300px; height: 300px; -webkit-transform: rotate(180deg); /* Safari */ transform: rotate(180deg); } </style>