<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<rect x="50" y="50" height="100" width="100" stroke="black" fill="yellow">
<animate
attributeType="XML"
attributeName="height"
begin="0s"
dur="10s"
from="100"
to="200"
repeatCount="indefinite"
/>
</rect>
</svg>