Recently the spin of the electron has become the focus of a new direction in electronics—semiconductor spintronics—which utilizes mechanisms of strong mutual influence of magnetic and electrical properties in magnetic semiconductors. These mechanisms are still a matter of considerable debate; however, all of them involve a concept of magnetic polaron—a microscopic cloud of magnetization made of several neighbouring magnetic ions and a carrier(s)—which determines most of the electrical, magnetic and optical properties of the material. Although a great number of experiments indicate the existence of magnetic polaron in magnetic semiconductors and related materials it has eluded direct observation until now. Using the positive muon as both a donor centre and a local magnetic probe, we have been able to generate and detect the magnetic polaron and determine its size in the magnetic semiconductor EuS.