How many years of college do you have to take to be a scientist?

I have a bachelor's degree of science in agriculture. I went to college for four years and majored in wildlife science. I am now a wildlife disease biologist. You can also get a master's degree which usually takes 2-3 additional years. To be at the top of your field, get a Ph.D. That will take 3 or more years extra, but sometimes you can go straight to a PH.D. without ever getting a master's degree. It all depends on how hardworking and intelligent you are (and also which field of science you go into).