In this lecture we review the basic principles and properties of neutrons as probes for fundamental and applied research studies. We outline the nuclear reactions used for neutron sources and neutron detectors and techniques of filtered neutron beams and time–of–flight. We summarize the interaction, transport and shielding of neutrons in matter. We concentrate on the reactions employed for detection of neutrons as well as on their interaction in silicon. We indicate the features of materials used as neutron converters and highlight areas with broad applications of neutrons