Callus and meristem culture are tissue culture techniques used to grow plant cells or tissues under sterile conditions. Callus culture involves growing an unorganized mass of cells from isolated plant parts on nutrient media supplemented with hormones. Meristem culture uses the apical meristem to regenerate whole plants and is effective for eliminating viruses. Both techniques require aseptically preparing explant tissues, using suitable growth media and hormones, and incubating cultures under controlled conditions to initiate cell growth. The cultured tissues can be used to regenerate plants, preserve endangered species, and produce plants resistant to diseases.