Biologists use imaging extensively for recording and documenting experimental results. It was not surprising, therefore, that the recent opportunities to search for extraterrestrial life resulted in discussions on the use of imaging and the instrument development required for this purpose. Imaging observations to detect extraterrestrial organisms have been made on lunar samples and meteorites and have been suggested for experiments on the surface of Mars. The observations made on the lunar samples are reported most extensively in The Proceedings of the Lunar Science Conferences. The investigators found no particles with morphologies suggesting biological origin, but did describe spheres with inclusions, dumbell-shaped particles, and actinomorphic forms. For the study of lifelike forms in carbonaceous chondrites, Urey (1962) suggested that "... biological and palaeobiological experts must study these forms in great detail, and their opinions should carry great weight in this problem." Such studies, however, resulted in conflicting opinons: Nagy et al. (1962) concluded that the organized elements were microfossils; Fitch et al. (1962) concluded that they were troilite, sulfur, or hydrocarbon globules; and, Briggs and Kitto (1962) found no evidence for ascribing either a biogenic or abiogenic origin for the microstructures. Urey (1966) later reviewed additional work, but the nature and significance of the organized elements was still not resolved. For detecting organisms in samples of martian surface materials, Lederberg (1960) suggested that microscopy be combined with histochemistry and spectroscopy. Since then, the science and methodology of this approach have been discussed several times, but the concepts have not been tested sufficiently to justify such an experiment. The lifeform recognition problem in relation to microfossils was discussed by Cloud (1965), who stated that "...the crucial point is not whether materials observed might conceivably be of vital origin, but whether they could have been produced by nonvital process ... Such hard-headed evaluation is