Baby awake in crib...

Tonight was the first night I noticed my LO awake, silently hanging out in her crib. Up until now, she's either been awake, crying, or alert kicking her legs up. Tonight she was just lying there staring out of the crib, not moving, just relaxing with her eyes open. She's only 3mo old.. Is this something babies do?

This might be a stupid question to a seasoned mother but I'm a FTM so please don't judge me harshly!