Meristematic tissues, or simply meristems, are tissues in which the cells remain forever young and divide actively throughout the life of the plant. When a meristematic cell divides in two, the new cell that remains in the meristem is called an initial, the other the derivative.
Meristematic cells are generally small and cuboidal with large nuclei, small vacuoles, and thin walls. A plant has four kinds of meristems: the apical meristem and three kinds of lateral—vascular cambium, cork cambium, and intercalary meristem.
There are three primary meristems: the protoderm, which will become the epidermis; the ground meristem, which will form the ground tissues comprising parenchyma, collenchyma, and sclerenchyma cells; and the procambium, which will become the vascular tissues (xylem and phloem).