sighing in his sleep

OK, so I still feel the need to verify that the poor kid is still breathing when I wake up in the middle of te night. At this rate, I'll be sneaking into his room when he's 16 and putting a mirror under his nose...
Anyway, I'm watching him while he sleeps and he does the funniest things. He'll have this great big sigh, or he'll grimace shaking his head from side to side - he'll even laugh in his sleep (he's giggling in his sleep right now while I wait for him to get into deep sleep before I move him to his bassinet)! I wonder what he dreams about. Let's face it - the whole "showing up at work naked/didn't study for the test/being chased by wolves" dreams are unlikely for someone who's nekkid a good bit of the time, doesn't know what studying or tests are, and thinks wolves are just another doggie. Does he dream about the goofy faces I make to get him laughing? Does he have nightmares about empty bottles or lost pacifiers? Makes you wonder...