A few nights ago I heard rustling on the baby monitor after we had put Sophie to bed, so I went in her room and found her like this: "Ta-da!! I learned to pull up on my crib mom!"
So I called Dave upstairs, and we got her out of bed so he could lower the mattress. Sophie thought it was super fun to go to bed and then wake up again to play. While she was crawling around on the ground in her room, she discovered the tipped over laundry hamper: