Physicists look for all the hidden laws that explain why all matter and energy in the known universe exists, where it comes from and how it behaves the way it does. Physicists use the laws they uncover to develop new materials, machinery, and technology to improve our lives and help us explore the universe further, from computers to telescopes and spacecraft. Physicists ask big questions, but they specialise in different areas and their work can be varied. For example, nuclear physicists study tiny particles of matter to discover what the universe is made of, whereas astrophysicists study some of the largest objects – stars, planets and celestial bodies. Many physicists also combine their work with the other sciences (chemistry and biology) to study things like meteorology (the atmosphere) and geophysics (the structure of the earth).