Not scarey

My two girls were having a conversation in the next room:
Miss 4: "I climb up my bookshelf to put things there."
Miss 11: "You CLIMB up your BOOKSHELF???"
Miss 4: "Yes, its a little bit scary"
Miss 11: "how do you do that?"
Miss 4: "The bookshelf is very heavy, it doesn't wobble. I'm small and it doesn't fall down"