The shoot apical and floral meristems (SAM and FM, respectively) of Arabidopsis thaliana contain reservoirs of self-renewing stem cells that function as sources of progenitor cells for organ formation during development. The primary SAM produces all of the aerial structures of the adult plant, whereas the FMs generate the four types of floral organs. Consequently, aberrant SAM and FM activity can profoundly affect vegetative and reproductive plant morphology. The embedded location and small size of Arabidopsis meristems make accessing these structures difficult, so specialized techniques have been developed to facilitate their analysis. Microscopic, histological, and molecular techniques provide both qualitative and quantitative data on meristem organization and function, which are crucial for the normal growth and development of the entire plant.