After a recovery period,
cells were fixed, permeabilized, and labeled with
antibodies that identify proteins that accumulate
at sites of DNA damage (red) and repair (green).
Note the easily identifiable red, green, and yellow
(co-localized) nuclear foci; these foci are often
only a few pixels in size. The image was taken
with a 40 x 0.9 NA objective and is a confocalmerged,
collapsed stack image.