Interesting question. I don't know exactly about becoming a scientist exactly, but I knew when I wanted to be an astronomer! I was on a winter nighttime snowshoe trip, the sky was clear, and Orion was rising. It was the most amazing, beautiful sight I'd ever seen and I decided right then & there to become an astronomer. I was 8. I also recall in highschool getting overwhelmed/bored/confused with all of the terminology in biology, and it reaffirmed that I just wasn't gonna do that!