No, I mean all of these 3 words are "laboratory" in English. What is the difference?

연구소 = research institute (of any kind). e.g. Bell Labs = 벨 연구소. Brookings Institution = 브루킹스 연구소.

연구실 = research facilities or room in a loose sense. Can indicate any type of research, such as politics.

실험실 = laboratory or lab in a specific sense, where tests and experiments are conducted. (실=real, physical, 험=experience,experiment).

Well

연구소 is a building where the laboratory is built in

And 연구실 and 실험실 are rooms for experiments

Speaking of how to call the places between 연구실 and 실험실

It would be depending on the decision which is made by ppl working there.

And in some cases ppl put specific names on the front of 연구실 or 실험실

E.g. chemistry lab =화학 실험실/연구실

Are you asking for Korean in the lab? 실험실