Plant growth throughout the life of the plant is a combination of cell growth (increased cell size) and cell division (increased cell number). The meristematic tissue (meristem) of the plant is responsible for the continuous growth through life. It is a type of plant tissue consisting of undifferentiated cells(meristematic cells) that can continue to divide and differentiate. Meristematic tissue is located in zones of the plant where growth can take place and because of that, there are three types of meristematic tissues: apical, intercalary (at middle) and lateral. Primary meristem allows growth in length or height (primary growth) and in woody plants secondary meristems allows growth in diameter (secondary growth).