Center
: A Petri dish with Pseudomonas aeruginosa growing on Cetrimide medium shows the diffusible fluorescent pigment pyoverdin. Macroscopic photography made by Elena Castillo, with a Canon eos-1n camera, Canon Compact-Macrolens EF 50 mm lens. See article by Bayó et al. this issue , pp. 87–90, on the vaginal microbiota. (The plate and the colonies are their actual size.)

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 cyanobacterium Halospirulina sp. Samples were frozen at high-pressure in a Leica EM Pact High-Pressure Freezer, and freeze-substituted at –90ºC 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 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 (http://www.ub.es/bemf) . (Magnification, ca. 4000×)