We review all aspects of the synthesis, properties, and applications of endometallofullerenes (EMF) over the last 20 years. EMF represent a new class of nanosized objects with specific physicochemical properties defined by the encapsulation of individual atoms and small molecules with significant potential of practical applications in biology and medicine. One such application is an EMF based anticancer drug capable of activating antitumour immune response, inhibition of the tumour development, and inhibition of angiogenesis and metastasis. Another, separate application direction is the use of EMF as contrast agents.