period talk

At what age is it good to talk to my daughter about periods ?! She's six and is very alert and real smart when it comes to learning new stuff . Recently , she pointed out my tampons and said they where for my "V" but she didn't really understand what it really was for so i just left it at that. Im just wondering whats a good age to give her that talk and i want to because my mom never really talked to me About periods and i was really confused when i first got mine lol