Fullerenes are molecules composed entirely of carbon atoms, arranged into structures similar to graphite, i.e., stacked graphene sheets of linked hexagonal rings; but they may also contain pentagonal (or sometimes heptagonal) rings. The rings then form nanoparticles of various shapes, such as hollow spheres, ellipsoids, and also cylinders (tubes). Fullerenes are important biologically active molecules with diverse effects on cells and tissues. They are able to oxidize biological molecules and cause serious damage to them, which can lead to cell malfunctioning, genome mutations and cell death. Simultaneously, fullerenes can act as reduction agents. Both the harmful oxidizing effects and the beneficial reducing effects of fullerenes can be exploited for preventing and treating various disorders. This book discusses the chemistry of fullerenes, as well as its natural sources and several technological applications.