In a research field, there are lots of small discoveries or developments, which nobody knew before, and contribute to moving the whole field forward. In terms of developments, applying the methods from Physics to Biological systems is something that many people have not done before, so for example, we used the same mathematics which led Einstein to predict the laser… to describe how cells interact with nanoparticles.
That’s really what we do! all our work is aimed at making a discovery that no one else has ever known before (sometimes they are small ones that people would probably think that was likely to work out that way), others are bigger ones that people really go- wow, we didnt think thats how that worked/happened. those are really exciting and usually built on lots of smaller discoveries.
To get your PhD thats what you have to do- discover new knowledge that no one knew before!
its all built on really careful design of experiments and repeated testing to make sure its correct!