Kief, Kef, Keef or kif refers to the loose, ried resin glands (or trichomes) of cannabis which may accumulate on containers, in grinders, or be removed with a kiefing screen or sieve. It is sometimes erroneously called pollen or crystal. Kief can be smoked in a number of ways, including using smoking pipes, bongs, vaporizers, or rolling papers (resulting in a joint). Kief contains a higher concentration of desirable psychoactive ingredients than ordinary preparations of cannabis buds from which it is derived. It may also be rubbed on the gums.