Hot off the presses: a stem cell paper connected to the disgraced Hwang laboratory in South Korea has been just retracted for misleading use of  photos that were claimed to be of different stem cells, but were actually the same (doctored) photograph.

The NY Times had a good article a few months ago on spotting doctored photos; Adobe Photoshop is a very useful tool in laboratory work so you can zoom in on areas of interest or clear up some noise. Astronomers also alter the color scales so X-Ray photographs, for instance, correspond to our visible spectrum (you’ll see how some beautiful photos of astronomical objects are called "false color"–this is an example).

Alas, these powerful programs can also be used for cheating.