Abstract: Microwave Kinetic Inductance Detectors, MKIDs, are a relatively new cryogenic radiation detector that can be optimized for radiation detection from the optical to mm waves. In this presentation I will focus upon radiation detection at millimeter and sub-millimeter wavelengths, for astronomy and cosmology. In both cases ultra-sensitive, large spectroscopic imaging systems are needed. MKIDs are especially interesting for such applications as they combine the required sensitivity with the capability to make 100.000 pixel systems with a limited amount of complexity. In this presentation I will present MKID technology and its application for future cosmological instruments, in particular the COrE mission, recently proposed to ESA.