This chapter introduces a simulation-based approach to create two- and three-dimensional (2D and 3D) computational plant models through simulations that mimic the growth patterns of real plants. When only plant structure is needed, the models are based on geometric rules and do not account for the functional aspects of plant organs, such as photosynthesis. The models provide a topological view in 2D and a realistic representation in 3D, applicable in multimedia and agronomy. The development of the plant structure is simulated through the activity of meristems, employing a botanical automaton, which simplifies the programming of plant development. The GreenLab model utilizes concepts like phytomers, transitions, and states to create a user-friendly interface for defining plant development parameters, including stochastic elements for meristem function. The chapter also discusses the experimental validation of plant development models across various species using the “crown analysis” method to estimate meristem function parameters from actual plant architectures. The results from their simulations are presented as computer-generated images, demonstrating the model's applicability and accuracy in studying plant architecture and growth.