This chapter discusses the integration of environmental factors such as temperature, light, water, and planting density into an eco-physiological context to monitor and predict plant development and stand production in greenhouses or fields. It emphasizes the transition from individual plant growth to stand simulation, highlighting the use of the leaf area index (LAI) and harvest index (HI) in agronomic crop models to estimate biomass production and yield. However, these models often overlook the root system and face challenges in calculating LAI under non-uniform planting densities. Structural–functional plant models (FSPMs) focus on detailed physiological processes within individual plants but do not address stand production effectively, using complex and costly techniques. The GreenLab model stands out by bridging the gap between agronomic crop models and botanical architectural models, offering compatibility with crop models, and enriching them with a deeper understanding of plant components, thereby providing new criteria for plant breeding and optimization of crop systems.