The availability of intense X-ray beams from synchroton storage rings has revolutionised the field of X-ray science. This is illustrated by the cover pictures: Von Laue's first observation of X-ray diffraction from a single crystal of ZnS used an exposure time of around 1000 seconds, whereas the diffraction from a single crystal of myoglobin using modern X-ray synchroton radiation was obtained within the duration of a single pulse lasting only 0.00000000001 seconds. In this book the basics of X-ray physics, as well as the completely new opportunities offered by synchrotron radiation, are viewed from a modern perspective. The style of the book is to develop the basic physical principles without obscuring them in too much mathematical rigour. This approach should make the book attractive to the wider community of material scientists, chemists, biologists and geologists, as well as to physicists who use synchrotron radiation in their research. The book should be useful both to students taking course in X-rays, and to more experienced professionals who have the desire to extend their knowledge into new areas.