The aim of this chapter is to give you a basic understanding of how stem cells function in plant development. Plants and animals lead quite different lives. Plants, for one, do not often move and cannot escape adverse environmental conditions. The most important consequence of their sessile mode of life is that plant development is not restricted to embryogenesis. Instead, it continues throughout the plant’s life, as it continues to grow and produce new organs. We will briefly discuss the implications of plant immobility on their developmental strategies, and how plant stem cell activity contributes to their indeterminate growth mode. Next, we will discuss the concept of plant meristems. These are highly specialized tissues that contain the plant stem cells and control both their maintenance and the production of new organs and tissues. Two main meristems are responsible for most of the growth in plants, the shoot and root apical meristems, and will be the focus of this chapter. We begin by reviewing the organization of apical meristems. Next, we discuss their embryonic origin, and we explore in finer detail the key signalling pathways involved in both the specification and maintenance of stem cell identity and activity. We will highlight the mechanisms that underlie the coordination of cell proliferation and differentiation. Hopefully, the concepts exposed in this chapter will provide you with a base from which to further explore stem cell activity and maintenance in plants, but also with the tools to draw interesting comparisons between animal and plant stem cells.