"After scientist Francis Crick discovered the structure of DNA, he penned a letter to his 12-year-old son describing what he and James Watson found."

From auction site: http://www.christies.com/lotfinder/lot/in-other-words-we-think-we-have-5665783-details.aspx?from=salesummary&intObjectID=5665783&sid=9629156b-4f2a-4708-8910-4526efc6a4de