Research on endohedral fullerenes has yielded unambiguous evidence for
the existence of selected inside-the-cage complexes. Milligram quanti
ties of purified samples of metallofullerenes have been produced, and
characterized via techniques that selectively probe the endohedral gue
st. Experiments aimed at a detailed understanding of the molecular pro
perties of the endohedral complexes as well as of the material propert
ies of compounds containing endohedral fullerenes have just started.