High Quality Content by WIKIPEDIA articles! Light sheet fluorescence microscopy (LSFM) or Selective/Single plane illumination microscopy (SPIM) is a fluorescence microscopy technique with an intermediate optical resolution, but good sectioning capabilities. In contrast to Epi fluorescence microscopy only a thin slice (usually a few hundret nanometers to a few micrometers) of the sample is illuminated perpendicularyl to the direction of observation. For illumination a laser lightsheet is used, i.e. a laserbeam which is focused only in one direction (e.g. using a cylindrical lens). A second method uses a circular beam scanned in one direction to create the lightsheet. As only the actually observed section is illuminated, this method reduces the photodamage and stress induced on a living sample. Also the good sectioning capability reduces the background signal and thus creates images with higher contrast, comparable to confocal microscopy.