Plant "stem" cells are also known as meristematic cells or makeup meristem tissue. The meristem cells are undifferentiated cells that can differentiate to become any other kind of cell with a specific function. The plant meristem is found at the tips of the shoots (root tip as well) and in the developing buds. In particular, the shoot apical meristem helps elongate the main plant stem so that a plant can grow upwards towards the light. Plants may experience secondary growth, or an increase of girth in their stems, which is promoted by having lateral meristem tissues in the stem.