Tissue culture refers to the method of artificial propagation of plants in which the cells or tissues are taken from a plant under sterile conditions. These cells or tissues are then kept in test tubes containing a culture medium, where they grow into an undifferentiated mass of tissue known as the callus. The callus is then transferred to another medium that induces the formation of plantlets. These plantlets can then be transferred to pots and grown into new plants. This method is used for the propagation of chrysanthemum, asparagus and orchids.