My 3 and a half yr old DD is currently very aware of all things female..v.interested in my make-up, teetering around in my 'high heels', talking about babies in tummies and going through the contents of my handbag and dressing table etc.
Consequently, she's come across my tampons and has asked me what they are, she's also spotted the string (sorry to be so graphic) when I'm in the shower. I'm ashamed to say I fob her off (something I always vowed not to do) then quickly divert her attention.
Presumably I've not got the only inquisitive little girl...how do the rest of you handle such questions at an early age?