A light microscopic technique that produces high-resolution images of fluorescently stained specimens without requiring elaborate preparation of the sample. The fluorescent markers (fluorophores), generally fluorescently labelled antibodies (see immunofluorescence), are excited by light from a laser focused by the objective lens of the microscope so that it scans a single plane in the specimen, creating an optical section, under computer control. At any moment the stimulating light is focused on a pinpoint and only emitted light from the same (confocal) point forms an image. This eliminates unfocused light and gives much greater resolution. The emitted fluorescent light is captured by a photomultiplier and assembled into digital images by a computer. Serial scanning of, say, an entire cell can thus visualize successive sections through the cell or create three-dimensional, or even time-lapse, images. Numerous fluorescent probes are available for labelling different components of cells or other material. The principles of fluorescence microscopy have been adapted in numerous related techniques so that the dynamic processes of living cells can be followed in space and time or assessed quantitatively. Moreover, computer algorithms now enable super-resolution microscopy (nanoscopy) with resolution greater than the limit of 200–300 nm achievable with conventional light microscopy. Hence, macromolecular or even molecular structures can be observed in living as well as dead specimens, avoiding the need for expensive and time-consuming electron microscopy, which necessarily uses dead material.