Glyoxal (OHC–CHO) is a dialdehyde that can be obtained from several natural sources, such as from the oxidation of lipids or as a by-product of biological processes.

Glyoxal has been the focus of much research due to its toxicology and as a fixative agent in biological research.

Paraformaldehyde (PFA) is the most commonly used fixative for immunostaining of cells, but has been associated with various problems, ranging from loss of antigenicity to changes in morphology during fixation. We show here that the small dialdehyde glyoxal can successfully replace PFA. Despite being less toxic than PFA, and, as most aldehydes, likely usable as a fixative, glyoxal has not yet been systematically tried in modern fluorescence microscopy.