Nearly all medical specialties use the scientific process of taking a tissue culture. There are three different types of tissue cultures: callus culture, a seed culture (used for plants), and embryo culture. A callus culture involves the removal of a small specimen from the body and facilitating its growth into a callus in a controlled environment outside the body in order to study it. A callus is a group or mass of unorganized cells. Usually, this is done in agar, a special nutrient-rich gel that feeds the specimen for optimal replication. Different types of micronutrients and macronutrients may be included, and basal salt mixtures may also vary to enhance growth. In dentistry, callus cultures can help professionals identify difficult to treat gingival bacteria or tumor tissue that grows from wounds in the oral cavity. When studied, the callus can help dental professionals develop an appropriately responsive treatment plan through trial and error.