What is CREDO Science? Cosmic-Ray Extremely Distributed Observatory (CREDO) — Citizen Science collaborative project which enables a strategy for a global analysis of cosmic-ray data to reach the sensitivity to extremely extended cosmic-ray phenomena, we call them Cosmic-Ray Ensembles (CRE), invisible for individual detectors or observatories. So far, the cosmic-ray research has been oriented on detecting single air showers only, while the search for CRE is a scientific terra incognita. We aim a