40 scientists have each contributed a piece relevant to their field - an elementary idea, a basic concept, a tool for thought. These pieces together form a tool-kit for the curious to use in extending their reading in scientific areas. The pieces are arranged in thematic groups: (1) Thinking about science (2) Origins (3) Evolution (4) Mind (5) Cosmos (6) The future. Each essay is short, averaging about 1500 words, and is self-contained, assuming no prior knowledge. Contributers include Lee Smolin, Alan Guth, Ian Stewart, Richard Dawkins, Steve Jones, Stephen Jay Gould, Lewis Wolpert, Freeman Dyson, Paul Davies and Martin Rees.