Mesoscopic physics is a field of study that deals with tiny things that are too small to see but too big to be explained by the laws of quantum physics. Think of mesoscopic physics as the middle ground between quantum physics and classical physics. It looks at things like electrons and atoms and how they behave in a variety of situations. It can explain things like why electrical current flows like it does in metals and why some materials have special properties that make them useful in things like electronics.