Cosmic-Ray Extremely Distributed Observatory (CREDO) is a scientific project initiated at the end of August 2016 by Polish scientists from the Institute of Nuclear Physics in Kraków (researchers from the Czech Republic, Slovakia and Hungary also joined the project) whose purpose is the detection of cosmic rays and the search for dark matter. Its aim is to involve as many people as possible in the construction of a global system of cosmic ray detectors, from which it will be possible to examine the essence of dark matter. Having a camera and a GPS module, a smartphone works well as a detector of particles from space.