  The detection of compact sources embedded in a background is a very common
problem in many fields of Astronomy. In these lecture notes we present a review
of different techniques developed for the detection and extraction of compact
sources, with a especial focus on their application to the field of the cosmic
microwave background radiation. In particular, we will consider the detection
of extragalactic point sources and the thermal and kinematic Sunyaev-Zeldovich
effects from clusters of galaxies.
