Electron micrographs of biological material are familiar to all biologists. This program illustrates the principles and techniques involved in the preparation and observation of biological specimens by transmission electron microscopy, techniques vastly different from placing a drop of pondwater on a slide and looking at algae. In this experiment, leaf materials containing different types of plastid are prepared for electron microscopy to provide insight into their ultrastructure, ontogeny, and interrelationships in respect to photosynthesis. Micrographs produced in the program and reproduced in the guide enable students to examine closely information on the development of chloroplasts and leucoplasts, the location of chlorophyll, and the effect of a herbicide which is a photosynthetic inhibitor; they should also be able to compare the various functions of light and electron microscopes. (15 minutes)