Old like Daddy

Leo and I were reading about neurons last night in his human body book. There's a picture of and embryo's neurons, which branch out a bit to become a fetus' neurons, which then branch out more to become an infant's neurons, and then a 20 year old's neurons. Then the branching reverses and at 40 years old, they look more like an infant/fetus's neurons and at 60 years old, there's hardly any branching at all. I explained to Leo that his neurons had a lot of branches now but when he got to be Daddy's age, they would get old and lose their branches. Leo said, "I hope I have long times before I am as old as Daddy".