Do Babies Dream of Seas of Milk

Some people talk about the golden moment, when the baby will smile or laugh at you. In the first week or so, we often find the baby smiling to himself in his sleep - dreaming of seas of milk? What do babies dream of, anyway? Siyuan is also active in his sleep, sometimes he would make noise almost like speech, or wave his arms and legs around, and then carry on sleeping. That led to us jumping out of bed every 20 minutes in the first week before we realized he's probably sleep-talking. Bizarre, huh?
Not sure if its normal, but by the end of the 2nd week and into the 3rd week, we find Siyuan smiling and even laughing more in his waking hours. And I'm pretty sure, he's sometimes laughing or smiling at us. Once, we were laughing at a joke, and he started smiling too. The other day, I stroked his hair, and he just broke out into a smile and laugh at me.
Moments to live for.