13 years old.

You are in a car, an enclosed space, with another person.  You know how those are the times you have conversations that are more in depth than the average garden variety?  More personal? Today that person was my son, Wilder.  We ended up in the car for 4 hours while taking my mom to the airport.  On the way home I was thinking about him, getting a little wistful, and I said,  "Sometimes I wonder what you will be like when you are an adult. What you will be doing, who you are."
Wilder: "Yeah, I wonder too. I wonder what my hair will be like."