Follow boy and girl twins as they learn what potties are for， struggle to make their potties work， wet their pants along the way then finally triumph。 Not only do they learn how to wee and poo on the potty， they also progress to the big loo！ Both an entertaining flap book and a practical guide， this book is invaluable for toddlers and parents。 Part of the bestselling award-winning series。 Other titles include What is poo？， What are germs？， What are stars？ and What is sleep？ Large sturdy flaps are perfect for little fingers。 With simple but informative text and charming illustrations on every page。