Meristems are specialised regions of active cell division in plants. The meristems represent the regions of growth. Growth is largely restricted to the meristem regions of the plant.  Depending on their location the meristems are of three types.

(i) Apical meristem:
These meristems are present at the tips of the roots and shoots. The shoot apical meristem is present at the tip of the shoots and its active division results in the elongation of the stem and formation of new leaves. The root apical meristem helps in the elongation or growth of roots. They are primary meristems as they appear early in the plant life. 

(ii) Intercalary meristem:
These are present between the masses of mature tissues present at the bases of the leaves of grasses. It helps in the regeneration of grasses after they have been grazed by herbivores. They are primary meristem.

(iii) Lateral meristem:
It appears in the mature tissues of roots and shoots. It is called the secondary meristem as it appears later in a plant's life. It helps in adding secondary tissues to the plant body and in increasing the girth of plants. Examples include fascicular cambium, inter-fascicular cambium, and cork cambium.