Those who are not shocked when they first come across quantum theory cannot possibly have understood it.
Niels Bohr

Quantum mechanics is commonly said to be a theory of microscopic things: molecules, atoms, subatomic particles.

Nearly all physicists, though, think it applies to everything, no matter what the size.

via Living in a Quantum World: Scientific American.

It is now thought to help migratory birds navigate, and to increase the efficiency of photosynthesis. Understanding how may lead to improved solar panels.