Physics is one of the key branches of Science along with Chemistry and Biology. It is the study of matter and energy and the interaction between them. Physicists investigate natural phenomena and try to make sense of the rules which govern the way the universe works. Physicists ask questions in order to improve our understanding of the very largest things such as the Universe itself, down to the very smallest things we know exist such as fundamental particles like quarks and leptons. Physicists also explore the coldest temperatures close to absolute zero and extremely hot places like the centre of stars. Understanding the laws of Physics enables quantum computers and fusion reactors to be built. Physicists make discoveries which affect the lives of all of us. Computers, air travel, cars, electricity in our homes and the internet are all hugely important in our lives today. These discoveries would not have been made without the passing on of knowledge throughout generations of physicists over hundreds of years.