Screen-based microscopes allow for a shared visualisation and task-directed conversations that offer significant pedagogic advantages for the science disciplines involving observation of natural samples such as the geosciences and biosciences, and particularly for distance education in these disciplines. The role and development of a virtual microscope used in the undergraduate teaching of geoscience at the Open University is discussed and then related to current developments in the collaborative web-based technologies and mobile computing. (Contains 3 figures and 1 table.)