There are over 275,000 different kinds of plant, ranging from tiny plankton visible only under a microscope to giant trees over a hundred metres tall. The stem supports the leaves and flowers of a plant. It also carries water, minerals and food up and down between the plant's leaves and roots. Water and minerals run up through the stem from the roots in thin tubes called xylem.
Food made in the leaves is carried down to the rest of the plant in tubes called phloem.
Many plants have stems that are green and bendy. Plants like this are called herbaceous plants, because many are herbs, such as mint and basil. Woody plants such as trees and shrubs have stiff stems or trunks covered in bark. Woody plants tend to have more xylem than herbaceous plants. A terminal bud grows at the tip of each stem, making the plant grow taller.