The theoretical basis of tissue culture is that plant cells are totipotent. The so-called totipotency means that any cell of an object carries a set of genetic information that develops into a complete plant. In vitro culture, this information can be expressed to produce complete plants. Although every living cell of a complete plant maintains its potential totipotency, it is relatively stable due to the limitations of its environment. This differentiation of plants is normal.

When in vitro tissues or organs are cultured in culture medium, these in vitro tissues or organs will undergo cell division and form highly vacuolated parenchyma cells in amorphous state, which is called callus. The process of callus formation from highly differentiated plant tissues or organs is called dedifferentiation of plant cells.