Kief is a powder made from the tiny potent crystals (sometimes called resin glands or trichomes) that form on the cannabis flower. Kief is a naturally concentrated form of cannabis that can be further intensified by extracting the crystals and using pressurized heat to form a crumble, commonly referred to as hash.
Though not as potent as BHO and other cannabis concentrates, kief concentrates remain popular because of their high concentrations of glands and the smoothness when inhaled or vaporized. There are many grades of kief depending on the qualities of the marijuana screened to create it. Like olive oil pressing, the screening process is a major determinant of quality.