In many disciplines surfaces are more important than bulk structures. Mechanical interac-tion between parts involves friction and wear between surfaces, many chemical interac-tions take place on surfaces (including catalysis), and most modern electronic devices consist of thin layers of materials laid down in intricate patterns on the surface of substrates. The appearance of objects is dominated by their surface characteristics, textures, and coatings. In all these cases and many more, scientists and engineers need to characterize surfaces and the ways in which fabrication and use modify them. Imaging plays important roles in obtaining the information as well as presenting it for human visualization and analysis. As Chapter 2 points out, human vision is well experienced at interpreting images of surfaces, and the presentation of various types of data rendered as a surface is a common data visualization tool.