It's often mentioned but it never explains what kind of research Walt's old company Gray Matter actually does in Breaking Bad. Am I missing something?
Based on the Scientific America on Walt's wall, Gray Matter made breakthroughs in Molecular Switches. *
Have a read here for a good overview of science. And Gray Matter. A synopsis:
From the text on the Scientific American cover and article, Gray Matter Technologies has been making significant advances in the field of molecular switches. Simply put, a molecular switch is a lot like a mechanical switch – it has two (sometimes more) states, analogous to on and off, and will change state when the environment is changed.
*shamelessly stolen from cde's comment on my own answer here.
Research, but beyond that it's not explained in the show
But it's actual purpose is unknown and not explored in the series.