Pixel microlensing is a special case of gravitational microlensing where the magnified source star is unresolved. The majority of stars in other galaxies cannot be identified individually because of their great distance from us. When they are magnified by a foreground object they may be detected as subtle enhancements in the otherwise relatively smooth surface brightness flux of the galaxy. Such events are commonly refered to as pixel-lensing events.
The detection of pixel-lensing events is a demanding technical challenge requiring special image processing techniques, such as difference imaging.