I have it hugely with DD2.
Today DD3 found a frog and DD2 said 'Mummy do we have a book about frogs because I want to know what's inside a frog but I can't see inside its head or its tummy?....' So, I quickly googled a picture of a frog's anatomy and printed it out for her. A few minutes later she came back with the picture and she'd written 'The frog - tongue, eyes, feet' on the top.
Then, she came to me about half-an-hour later and whispered 'Mummy, do you have a picture of a chicken like the frog one with the picture of the things that might be inside its head and its tummy?'
She was more animated about this than I've ever seen her about school...