In-vitro preservation refers to the preservation of plants in glass bottles. In a real sense it is tissue culture. Organic reproduction is the only way for species to reproduce , it is the only way to preserve those plants. Another method of in-vitro preservation is cryopreservation . In the cryopreservation reaction living organisms , such as plant-dividing tissues , cell protoplasts. In the case of embryos or single cells and animals, sperm , eggs , embryos, etc., can be stored at extremely low temperatures for a long time. Generally , all biological reactions and metabolic activities of stored organisms are suspended for a certain period of time by keeping the liquid nitrogen in a very cool state (-198 C ). Proper care is also taken to ensure that the preserved organisms are not destroyed. In this process the preserved organism is revived without any harm. It is currently the most common in-vitro preservation method. At present the usefulness of cryopreservation method is being observed in the development of fisheries resources in our country. Silver carp , common carp , rui , katla and mrigel fish are seen to be useful in this process. It is to be noted that the sperm conservation of buffalo in Bangladesh is going on successfully. In many countries around the world, gametes and embryos of endangered species and all animals that play a role in the economy are being preserved for a long time through cryopreservation.