Tissue culture is the propagation of plants through "cloning," an asexual method. The process consists of growing a portion of the original plant in vitro (an artificial environ ment), promoting its multiplication, and then transferring it to potting medium in a greenhouse environment. Tissue culture is based on the concept of totipotency, which is the ability of a cell, given the correct environment, to develop into a new organism due to the genetic information contained within the cell. Because the new organism has exactly the same genes as the original, it becomes an identical twin to the original. Plants have been propagated asexually for thousands of years by means of cuttings, divisions, and grafting. Tissue culture adds a new dimension to propagation by providing a means of rapid multiplication in a short time span while utilizing a small quantity of plant tissue. Starting with 50 Boston fern explants (runners), approximately 6,250 Boston fern plants may be produced in 12-18 weeks. Tissue culture is currently being utilized to commercially propagate many plants including Boston ferns, hyacinths, lilies, caladiums, orchids, and gerbera daisies. It is used not only to mass-propagate plants economically, but also to produce pathogen-free or disease-free plants, plant mutants for crop improvement, plant hybrids, and plant products such as steroids, titerpenes (ginseng), and antitumor alkaloids. The concept of tissue culture and totipotency has been included in introductory plant sciences for many years. Now as instructors, we have the information, materials, and usually the space to take tissue culture out of the textbook and into the laboratory. Teaching the theory behind tissue culture is good, but providing our students with the actual experience is even better. Tissue culture can be used as a vehicle to present other concepts related to the growth of plants in general, such as sterile technique, hormone balance, anatomy, and environmental factors. Practicing tissue culture teaches students more than just how to rapidly multiply plants. Tissue culture utilizes basic sterile techniques; poor technique is usually apparent in 4-6 days. This visible contamination is an indicator to the student of the lack of good procedure, and is usually visible soon enough after the begin ning of the procedure to allow the student to start again. The relationship between phytohormones, auxin and cytokinin, in the promotion of shoot versus root growth becomes apparent as the plant tissue is transferred from one growing medium to the next. The various stages of culture require different media. The media contain inorganic nutrients, sucrose for cellular respiration, vitamins, and growth regulators in varying combinations. Through learning the process of tissue culture, the student will also become aware of which part of a particular species is most amenable to in vitro growth. Tissue culture can utilize almost any portion of a plant as the explant: flower parts, buds, runners, stem sections, bulb sections, leaves, or roots. Tissue culture can also make the student aware of the need for specific environmental conditions for growing plants. The medium provides the essential nutrients for growth inside the test tube. The enclosed test tube environment maintains the proper humidity. Light and temperature are factors that must be regulated to en sure optimal multiplication and growth of the plants. During the various stages of growth and multiplication, the cultured plants require different light intensities. The final stage is the growth of the new plants under controlled greenhouse conditions including humidity and light intensity until the root systems are fully developed. Temperatures for the early stages are usually kept constant.