She only smiles when she sleeps

I will hold her, and she will just stare into my eyes, I swear I have never experienced anything like that in my life. It is neat because she looks a lot like me, and the fact that she is MY daughter makes the baby holding a experience much different. Her facial expressions are limited to "I'm really full right now" and "I'm really hungry/upset right now." When she is falling asleep or in REM sleep, she will do these random other facial expressions. This is the only time I ever see her smile. I am really enjoying this infant stage of her life, to hold her and talk to her as she looks at me is so wonderful. But I can't wait until I smile or laugh, and she smiles and laughs back.