Synthetic polymers make excellent specimens for light microscopy. Despite this, the use of the technique, at least in its advanced forms, is not so widespread as might be expected. Although reliable and relevant data are difficult to find and quantify, it seems that in other fields of materials science and technology there is a greater readiness to tum to the microscope in research, in industrial problem solving, or for quality assessment and control. It also seems that the reasons for the present situation are partly historical, partly the result of the structure of the plastics and rubber industries, and partly the education and training background of senior staff who tend to be chemistry or engineering based. In neither field does light microscopy feature strongly in the basic training. The primary aim of this book is to provide some insight into the range oflight microscopy techniques applicable to polymeric specimens, and to highlight typical applications to commercial polymers and polymer products. Where appropriate, the optical techniques involved are discussed in some detail. However, it has not been the intention to produce a light microscopy textbook dealing with the principles and design of the basic instrument. Many such texts are available, and selected examples are cited in the reference list at the end of most chapters.