From the programme:
A wealth of information relating to the nature of crystals can be gleaned from an examination of the symmetry and other striking physical characteristics of minerals and gemstones. Especially revealing are their optical, thermal and electrical properties. Coloured solids, be they fashioned by Nature over geological time or in the laboratory on the scale of human activity, as well as the luminescence induced within them by illumination with ultra-violet light or electrons, tell us a great deal about the interior of crystals and about the nature of light itself. In turn, by probing a few other properties of both familiar and unfamiliar minerals and man-made crystals, we can understand the processes entailed in creating colour, in the emission of light and, in particular, in the contrast between incandescence and laser action.
John Meurig Thomas and David Phillips
How does a crystal look like up close? John Meurig Thomas uses optical and electron diffraction to reveal the crystal architecture and explains how the architecture of proteins links to their function.