In 1993, it was discovered that when C 60, a spherical molecule consisting of 60 carbon atoms, is exposed to noble gases at high pressure, complexes such as He@C 60 can be formed (the @ notation indicates He is contained inside C 60 but not covalently bound to it).
I 1993 blev det opdaget, at når C60, et sfærisk molekyle bestående af 60 carbonatomer, bliver udsat for ædelgasser ved højt tryk, kan komplekser såsom He@C60 dannes (@-notationen indikerer, at He er inden i C60 men ikke kovalent bundet til det).