As Russell said The word matter is, in philosophy, the name of a problem and our scientific investigations and philosophical inquiries show that it becomes more and more complex and interesting as we study it. This book seeks to show how ideas of matter have developed from Democritus to Heisenberg. The problem of matter may well be insoluble but at least we can begin to appreciate the mystery of what is so often taken to be the mundane 'stuff' of common sense.