The question of what is matter has fascinated the human race for thousands of years, and continues to fascinate us today: what is it made of, and how does it behave? Early in our history, the character of natural materials was of critical importance to us, and it is no accident that we date the prehistory of humanity by the materials with which our predecessors made their tools. Tools are one of the more enduring creations of our prehistoric ancestors, and are of particular historical significance as they document the increasing technological sophistication of the human race. From the Stone...