Answer from Marsh Maven, a Marine Biologist:
That depends on what you want to do. You will definitely need to go to college for 4 years. But depending on the field you go into, you may have to go to graduate school once or twice to get a Masters degree or a PhD. This could take an additional 2-8 years. But from my experience, during this time you usually get to do some really neat things that a regular job wouldn't let you do. You should think about what it is that you want to do and then find out what kind of education you will need. Being a scientist is often a labor of love, you need to really enjoy it first before you can worry about the amount of educational commitment it takes.

Thanks to Christina from Healey Middle School for submitting this question!