I'm not sure what is considered groundbreaking science, but a lot, a majority of science even, is not groundbreaking. But offhand, the ISS provides us the abili

I'm not sure what is considered groundbreaking science, but a lot, a majority of science even, is not groundbreaking. But offhand, the ISS provides us the ability to monitor the difference that microgravity has on humans, eg the twin study they've done as well as other studies on blood pooling and muscle loss. If we plan to ever have long term missions in space, like Elon Musk and his mars aspirations, then the ISS is an important stepping stone to understand the implications on human health and experience managing humans in space. It's pretty easy using Google to find some of the research that people have thought was notable: https://www.sciencefocus.com/space/five-things-the-iss-has-done-for-us/ https://www.sciencefocus.com/space/five-things-the-iss-has-d... https://www.nature.com/articles/d41586-020-03085-8 https://www.nature.com/articles/d41586-020-03085-8