This is a full review of the treatment of science and technology in museums. It discusses the nature of science and its cultural standing at the end of the 20th century as well as the history of science museums in Europe and North America and the effects upon them of the heritage phenomenon. It also includes much of strictly practical interest: it reviews and compares the very best of modern practice - in San Francisco and Toronto, in London, Paris and Berlin; it discusses the technical problems of displaying working machinery and of interpreting unfamiliar and difficult concepts for the public; it explains the principal approaches to collection management and draws lessons from all over the world to compile a thorough appraisal of the effects of the new market-orientated, consumer-led philosophy on the content and practices of science museums.