Here we present ScientificAmerican.com's most-viewed slide shows of 2008. Some photographs reveal what is not visible to the naked eye, such as the Nikon Small World and Olympus BioScapes contest winners. Mind Matters highlighted the science behind the optical illusions in movement, art and in eyes themselves. Hany Farid revealed famous tampered photos from history. David Biello led a tour through a house that runs on hydrogen and solar power. Computer-generated images revealed a new way to look at election results and the map of the United States. Other slide shows showcased gadgets to give as holiday gifts or designed to make a difference in the world.