Aaah my 13 month old has taken to playing with his private parts. What's the best way to react?

there is no need to react. for your baby, playing with the private part is as regular as playing with his hands or legs and any other part of the body. it is us adults who think it is something embarassing or something that needs to be taken care of. let your baby explore his body and soon he will get over it. just make sure he always wears his pants especially when anyone else is around.