Center: Part of Diego Rivera’s 1952 mural “Water, origin of life”, which was painted on the walls and bottom of the Lerma River Supply System, in Chapultepec Park, in Mexico City. It is an unique underwater mural painting about which Rivera wrote: “At the bottom of a large reservoir, I painted varieties of protoplasmic life. These evolve, on the lower portion of the perpendicular walls, into more complex forms, culminating in a nude man and woman, the final creations of the mural." [D.R. © 2003 Banco de México Diego Rivera & Frida Kahlo Museums Trust. Av. Cinco de Mayo No. 2, Col. Centro, Del. Cuauhtémoc 06059. México, D.F., and reproduced by permission of the Instituto Nacional de Bellas Artes y Literatura.] The recently restored paintings are not yet opened to the public. See article by S. Islas et al., this issue, pp. 87–94, on “Hyperthermophily and the origin and earliest evolution of life.” (Scale, ca. 0.04)

Upper left: Three-dimensional reconstruction of the Infectious Bursal Disease Virus (IBDV), from chicken, obtained by image processing from cryo-electron micrographs of purified virions. The resolution is 2.8 nm. Authors: José Ruiz Caston, Francisco Rodríguez and José L. Carrascosa, National Center for Biotechnology, CSIC-UAM, Madrid, Spain. (Magnification, ca. 1,300,000×)

Upper right: The bacterial community at the sediment–water interface of a stratified lake (Burke Lake, in the Rose Lake recreation area, near East Lansing, Michigan). Phase micrograph by Douglas E. Caldwell, University of Saskatchewan, Canada. (Magnification, ca. 1100×)

Lower left: The wood-digesting symbiotic protist Joenia annectens from the European dry wood-esting termite Kalotermes flavicollis. Phase contrast image by Michael Dolan, University of Massachusetts at Amherst, USA. (Magnification, ca. 3100×)

Lower right: Histoplasma capsulatum FMR6518. Mature macroconidium with club-shaped ornamentation. Scanning electron micrograph by J. Gené and M. J. Figueras, University Rovira Virgili, Reus, Spain. (Magnification, ca. 5300×)