© 2014 by Taylor & Francis Group, LLC. Through convergent evolution, both plants and animals have come to rely on stem cells to generate and maintain body plans. Many of the mechanisms required for the regulation of stem cells are similar between plants and animals. This chapter highlights the current state knowledge about stem cell regulation of plant development and de novo formation of stem cells during regeneration and lateral organ formation. Studies discussed specifically focus on two classic plant model organisms, Arabidopsis thaliana (Arabidopsis) and Physcomitrella patens (Physcomitrella). Arabidopsis and Physcomitrella are land plants that are part of the angiosperm and bryophyte (moss) families, respectively. Both types of plants have a morphological.