It's impossible to know where you will be in 5 years but do assure the interviewer that, given all possible circumstances, you could see yourself as a long-term fit for their position. You can show the interviewer how driven you are when you answer this but be sure to remain realistic to typical industry growth.
"Ideally, 5 years from now, I would love to see myself growing into a more prominent leadership role within the lab. My career interests align very nicely with your facility's goals which helps me to see a great long-term fit here."
Entry Level answer example
"If I am given the opportunity to join your clinic, I do see this as a long-term fit for me. Further down in my career, I would like to advance into a leadership role while remaining laboratory based."
Experienced answer example
"5 years from now, I would like to be supervising or managing a team of my own. I feel like I am progressing at a rate that will make this a possibility."