This bed is super cute but pretty bulky for a twin sized bed. We obviously put a twin mattress inside, (which sits directly on the floor) and there are several inches of space between both sides of the mattress and the actual bed frame. The bed should at least have some type of slat or platform for the mattress to sit on in my opinion. The bed was pretty easy to assemble. The part that took the longest was placing all of the decals onto the bed. Anything other than the black plastic is stickers that you put on yourself. It is super cute though and my four year old is now excited to sleep in his own bed!