The BioPulverizer reduces tissue hard-frozen in liquid nitrogen to a fine powder. Because of the high water content, most fresh tissue becomes as brittle as glass at liquid nitrogen temperatures. A sharp blow with a hammer will shatter it into tiny pieces. Called freeze-fracturing or cryopulverization, the method is especially useful for preparing tough, fibrous tissues such as skin, cartilage, cornea, etc. for subsequent rapid cell disruption using other techniques. The Bio-Pulverizer consists of a hole machined in a stainless steel base into which fits a special piston, or pestle. In a typical procedure, up to 10 g of animal or plant tissue is hard-frozen in liquid nitrogen and placed in the pre-chilled BioPulverizer. The piston delivers a blow to the brittle tissue reducing it to powder. Freeze fracturing with the Bio-Pulverizer is also useful for extracting labile tissue metabolites. Place the BioPulverizer in a shallow container and cool thoroughly with either liquid nitrogen (preferred) or a dry-ice/alcohol mixture (next best). Place prefrozen tissue in the well of the mortar. Remove the mortar from the shallow container, place it on the lab bench and pulverize the tissue with one or two blows to the pestle with the hammer. The mass of the stainless steel will preserve the cold long enough for you to complete your pulverization without adding additional liquid nitrogen. Empty the powdered contents for subsequent homogenization or extraction procedures.