Humans have large brains, and proportionately large heads, compared to all other mammals. As such, we are born earlier than we would ideally be – because waiting until we were really ready to come out of the womb would mean we were too big to pass through the birth canal. (Perhaps this goes without speaking, but I’m referring to “us” as a species here, not on any one individual.)
People often refer to the first three months of life as the fourth trimester, a term popularized by Dr. Harvey Karp (author of The Happiest Baby on the Block). Generally speaking, this is a critical period of development that the brain and central nervous system need to mature. In the course of those first three months, an infant develops into a baby who is able to respond to the outside world, regulate their breathing, lift their heads, smile, coo, and interact socially in ways that are (arguably) necessary for survival.
Today, Oliver crossed that threshold. Happy 3 month birthday, Little Man.