Cozy Natural Sleeping Surface! Your baby is in for a real cozy sleep on this mattress. Made with Certi-PUR-US® certified, ecologically friendlier foam, you can be sure your baby is safe from harmful toxins. The firmer side is idea for your baby's development, where the softer toddler side is super comfortable. The organic cotton cover with waterproof backing, puts soft cotton closest to baby's delicate skin.