Book about bodies (including how babies are made!) for preschooler

[superking]

My DS has become increasingly curious about how babies are made since DS2 was born earlier this year. So far I have tried to explain things to him/ answer his questions in an age appropriate way, but each answer just seems to prompt another, more complicated question and I am starting to feel a bit out of my depth!

We also haven't really had a proper talk about how girls and boys have different bodies yet either, so I'm thinking that a book that covers all of this would be a good idea to help me approach these conversations.

Does anyone have any recommendations? DS is 3 and a half.

I've just read Where Willy Went by Nicholas Allen with my 4yo, who was asking lots of questions. It's just the right level - it doesn't shy away from reality too much but is age appropriate, and funny. It has a really good page showing how the cells divide and turn into a baby, which my DS was fascinated by. I would recommend it.