Three reactor experiments (NEOS, STEREO and DANSS) have recently published their first results of the search for sterile neutrinos. MINOS, MINOS+ and IceCube have also set stringent constraints on the parameters of the four-neutrino flavour oscillation model. Several dedicated experiments are either in the phase of construction or are being planned. In the seminar I will answer the question what is behind the considerable interest in the not new idea of sterile neutrinos.