Quantum physics concerns the behavior of the smallest things we know. These smallest things are very small indeed. Although the world of the very small is remote from our senses, it shapes everyday experience.Almost everything we touch and see (together with nerve impulses and light, the messengers of touch and sight) owes its character to the subtle architecture of atoms and molecules, an architecture whose building code is quantum mechanics. And when we come to large-scale phenomena that depends in a direct way on the details of atomic processes-for example lasers, superconductors, and solid-state electronics-then the explicit use of quantum physics is essential.