I wish I had something substantial to add, but I was just in awe by the presentation, the clear-cut contact information and credentials laid out, the pleasant font choices and how the related stories weren't pushed on you as opportunities for ad-rev, but for enlightenment for the curious.
If you're in London, they also have the Wellcome Collection - a medical focused museum that describes itself as "The free destination for the incurably curious". Pretty much always fascinating and worth a visit!
http://www.wellcome.ac.uk/ http://www.wellcomecollection.org/
What you do is take blood from one of about 10 small testing segments and mix it with the recipient's serum. If it clots or hemolyzes, that's bad. That's the most elementary method of crossmatching units, and it's often still done just before sending a unit out, because the blood's there to be tested, might as well.