The recent accounts in the media that an Italian researcher had uncovered tiny letters in the eyes of the Mona Lisa seemed suspicious, especially since in no account that I have seen has anyone bothered to print a picture of the supposed micro-signature. Well, Joe Nickell has seen this sort of claim before, and he has some background on the people who are making this extraordinary claim. (Spoiler: They harbor all manner of improbable beliefs.)
RJB
Skeptical Humanities 