Center: The aphid Cinara tujafilina (Insecta: Hemiptera: Aphididae) that harbors a bacterial symbiont, Buchnera, with one of the smaller prokaryotic genomes known. See article by J. Sapp, this issue, pp. 145–150, on “Paul Buchner (1886–1978) and heredity symbiosis in insects.” Courtesy of A. Latorre and J.M. Michelena. University of Valencia, Spain. (Magnification, ca. 30×)

Upper left: Human calicivirus (Norwalk-like virus). Transmission electron microscopy (negative staining with phosphotungstic acid) by David Cubitt, Great Ormond Street Hospital, London, and Albert Bosch, University of Barcelona, Spain. (Magnification, ca. 650,000×)

Upper right: Cross section of a high-pressure freezed and freezed-substituted sample of the cyanobacterium Halospirulina sp. Samples were frozen at high-pressure in a Leica EM Pact High-Pressure Freezer, and freeze-substituted at –90°C for three days in a Leica AFS instrument (Xavier Huete, Jordi Urmeneta and Carmen López-Iglesias, University of Barcelona, Spain). (Magnification, ca. 35,000×)

Lower left: Nuclear and infraciliature features of the ciliated protozoa Colpoda inflata, observed by silver carbonate impregnation. This strain was isolated from a soil sample from a Panama forest. Courtesy of Carmen Jareño and Ana Martín-González. University Complutense of Madrid, Spain. (Magnification, ca. 1000×)

Lower right: Basidia of Lentinula edodes. Scanning electron microscopy image of a fertile gill’s surface showing 4-sterigmated basidia, some with developing spores. The mushroom fruited at the Bank of Edible and Medicinal Mushroom (BEMF), University of Barcelona, Spain (http://www.ub.es/bemf). Courtesy of Enric Gràcia, University of Barcelona, Spain. (Magnification, ca. 4000×)