Mortars are valuable grinding vessels used since ancient times in preparation of crushed and ground samples for experimentation. These can come in a variety of forms, including those used by hand, in conjunction with a machine, or after being frozen with liquid nitrogen for use in procedures dealing with frozen tissues. Mortars, and particularly mortar grinders, are ideal for grinding dry samples and solid materials in suspension, and for manufacturing and homogenizing pastes and creams to laboratory standards.