<!DOCTYPE html>
<svg width="100" height="100">
  <pattern id="outer" width="1" height="1">
    <pattern id="inner" width="1" height="1">
      <rect width="100" height="100" fill="url(#outer)"/>
    </pattern>
    <rect width="100" height="100" fill="green"/>
  </pattern>
  <rect width="100" height="100" fill="url(#inner)"/>
</svg>
