The XSL-FO Output

<?xml version="1.0"?>
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">

  <fo:layout-master-set>
    <fo:simple-page-master master-name="only">
      <fo:region-body/>
    </fo:simple-page-master>
  </fo:layout-master-set>

  <fo:page-sequence master-name="only">

    <fo:flow flow-name="xsl-region-body">
      <fo:block font-size="20pt" font-family="serif"
                line-height="30pt">
        Hydrogen
      </fo:block>
      <fo:block font-size="20pt" font-family="serif"
                line-height="30pt" >
        Helium
      </fo:block>
    </fo:flow>

  </fo:page-sequence>

</fo:root>