Data which is the smallest element of a digital image or data array.

A pixel is often thought of as rectangular; but it could have any shape. As the term pixel originated from digital images care needs to be taken when using the term in experimental science where it can be often connected to a real physical meaning.

Note that a pixel might be the result of temporal and/or spatiotemporal integration. A detector pixel represents an area over which a signal, that is projected onto the detector plane, is spatially and temporally integrated and converted into a digital image pixel value.

When recording a data frame in electron microscopy using multi-pixel detectors, the spatial ordering of pixels follows the ordering of the detector pixels. In the case of a single pixel detectors, the pixel ordering follows the beam dwell and sampling positions. A higher effective pixel density might be necessary to represent this within a typical rectangular pixel arrangement. The pixel shape typically follows from the sampling grid, hence it does not have a physical relevance.