Large millimetric and submillimetric telescopes can play a crucial
role in our understanding of the Universe, allowing the direct
measurement of early galaxies or the investigation of the earliest
stages of star formation. The B modes of CMB polarization are a
direct probe of the Inflationary epoch and their measurement
promises to provide information on the scale of energies at which
the process took place. For these investigations (and many
others), large detectors arrays with thousands of pixels are
needed, to achieve high mapping speeds. This is especially true in
the case of mm and sub/mm observations from extremely cold and dry
locations like Dome-C, where ultra-low temperature detectors,
reaching photon noise limited performance, are needed to fully
exploit the excellent quality of the site. In this paper we
present the working principle of the Microwave Kinetic Inductance
Detectors and their status of development in Italy, focusing on
the key aspects that make them ideal for large arrays of sensors.