http://www.npr.org/blogs/thesalt/2012/08/29/160274163/introducing-microgreens-younger-and-maybe-more-nutritious-vegetables
Great article from NPR's blog, the salt.
Basically, the article says that current nutrition studies indicate that microgreens may pack more nutrition than other vegetables.
I've got several trays of sunflower greens growing right now. We love them in salads. Delicious!