I don't know how it happened, and I'm not sure exactly when, but this little lady is sitting up on her own now.
She can't get into that position herself, and will fall over at a moment's notice. But this morning she sat in the middle of our bed while we both got dressed, and for quite some time after. All on her own. While we just stared and marveled.
Playing with a baby that can sit? Yeah, it just got a lot more fun!