He smiles in his sleep.
It could be that his brain is tapping connections to force his tiny, new muscles into exciting patterns of movement, or it could be that he's dreaming newborn dreams of warmth and light and caress, or it could be that he's feeling the burst of a wayward air bubble as it travels through his squishy belly.
Does it really matter?
He smiles in his sleep, and I smile at his purity.
I think I smile in my sleep these days, too.