Sitting up on his own

I have yet to see him actually do it, but Lars can now sit up on his own.  On Sunday I was working on taxes and Lars crawled over to play with some papers I put on the floor for recycling.  Next thing I knew, I looked down and he was sitting up and playing with the paper.  This morning I was cooking breakfast and when I left the room Lars had been crawling around, but when I came back, he was sitting up.  Good thing I dropped the cribs to the lowest level yesterday, he'll be pulling up in no time flat!