Confocal microscopy, especially in combination with fluorescent probes, is often used to examine optical sections from fairly thick biological specimens. The digital image presented below features autofluorescence of a butterfly wing scale (illustrating the striated surface structure) captured in a thin optical section with a confocal laser scanning microscope.

Butterfly Wing Scale Specimen: Butterfly Wing Technique: Confocal Autofluorescence

Optical sectioning enables serial portions of the butterfly's wing to be examined under the microscope to the exclusion of other parts of the wing. In confocal microscopy, the image-forming light from a given focal point can be seen through the microscope, while any out-of-focus light is excluded by a pinhole aperture. This "slice" is termed an optical section.