<ForeignObject>s

Non-SVG elements, such as XHTML and MathML can be placed onto SVG canvas using <foreignobject>
The foreign objects will be inserted at correct place in drawing order

  <svg xmlns:html="http://www.w3.org/1999/xhtml"
          xmlns="http://www.w3.org/2000/svg" >
    <circle ... />
    <foreignObject x="2cm" y="3cm" width="8cm" height="4cm">
      <html:div style="background-color:yellow; font:40pt sans-serif;" >
        The quick brown fox jumps over lazy dog
      </html:div>
    </foreignObject>
    <circle ... />
    <circle ... />
  </svg>

The quick brown fox jumps over lazy dog