When considering why microscopy methods should be used in cement and concrete science, a rather simple answer is that cement is a microscopic material: a grey powder whose grains range from around 100 μm down to less than 1 μm in size. However, its end uses, in concrete, are anything but microscopic and include some of the largest manmade structures. The challenge is to link the microscopic to the macroscopic and here microscopy has a role to play. Microscopic study can be expected to give an insight into the following three areas: • An understanding of reaction mechanisms. • A diagnosis of damage processes. • An insight into microstructural property relationships. In all of these cases microscopy can only supply partial answers, which must be integrated with results from other techniques into a coherent conceptual or theoretical framework. In the first two cases, qualitative examination of the microstructure, perhaps combined with local chemical analysis, may be sufficient to indicate or confirm a mechanism. The last of these three goals is perhaps the most difficult, as here, some kind of quantitative measure of the microstructure is necessary1. Yet understanding the links between microstructure and properties is the essential precept of materials science, necessary if the development of cementitious materials is to be anything other than empirical. Obtaining numbers from images is the goal of image analysis.