Scientists and technicians use a huge variety of instruments and tools in their work ranging from the small, simple and cheap to the large, complex and extremely expensive nuclear research reactor or satellite that requires a large team to build and operate it. Instruments allow scientists to measure and observe things they cannot directly see for themselves such as the atomic structure of materials or the flow of air over an aircraft wing at transonic speed. Learning to use new instruments was an important part of training to be a scientist and getting good results often relied heavily on a willingness to spend many hours first perfecting these skills and then using them to collect data. Some instruments were bought from commercial suppliers, but often scientists doing new kinds ofresearch needed to use their own ingenuity and expertise to design specialist equipment or adapt existing instruments to a new purpose. Computers have become the single most important tool for scientists and engineers across the range of disciplines and revolutionised their ability to analyse and process data as well as to use that data for practical purposes.