What major wouold be good if you want to do medical research as a career? (i.e. chemistry, biotechnology, maybe a discipline of engineering?, etc) I’m especially interested interested in neurology and stem cell research. I understand that one would definitely have to get a Ph.D, but what would be a good major to start out with as an undergrad and why? Responses are appreciated! 
Most of the people I know in biotech & biomedical research started out in some kind of bio-science (general biology, biochem, human nutrition, etc.) and then specialized later in grad school.
Do a quick google for the research projects you are interested in, and find out who the principal investigators are. Then look up their educational histories. That will give you a notion of where you could start.
Medical research is such a broad field that it would really depend on what kind of medical research you want to do. If you want the more biomedicine/biomedical side then the traditional majors are biology, chemistry, biochemistry or some mix thereof. If you want technical applications to medicine lots of people go for computer science, math/statistics, physics, or engineering. Any and all of the above do research in neurology/neuroscience and stem cell research.
(And some people study the social science of medicine and major in history, psychology, sociology, anthropology, or political science in undergrad, but that’s probably less applicable here.)