I am already grown up (my growth plates have been gone for over two years).
When I was younger (age 3-6), I wanted to be a paleontologist. After that, I wanted to be a physicist. Then I studied astronomy and considered that as a possible field. At age 11, I wanted to be a chef. After a year, I settled on some sort of scientific research, either chemical, physical, or biological.
The 6 years after that were devoted to deciding which of the three I would go with. I chose biology, but continued researching/studying other fields on the side.
I'm pretty good at cooking today, though.