My main interest is the problem of the singularity. If we can't understand what happened at the singularity we came out of, then we don't seem to have any understanding of the laws of particle physics. I'd be very happy just to understand the last singularity and leave the other ones to future generations.
Quantum physics forms the foundation of chemistry, explaining how molecules are held together. It describes how real solids and materials behave and how electricity is conducted through them... It enabled the development of transistors, integrated circuits, lasers, LEDs, digital cameras and all the modern gadgetry that surrounds us.