The difficulty of predicting the emergent development, homeostasis and disfunction of tissues from cells’ molecular signatures limits our ability to integrate molecular and genetic information to make meaningful predictions at the organ or organism level. Virtual Tissues are an approach to constructing quantitative, predictive mechanistic models starting from cell behaviors and combining subcellular molecular kinetics models, the physical and mechanical behaviors of cells and the longer range effects of the extracellular environment. For the past 15 years, we have been developing Virtual-Tissue tools (CompuCell3D) to bridge the gap between molecule and physiological outcome [1]. I will illustrate these approaches in: 1) the development and degradation capillaries in the retina of blood vessels and their roles in Choroidal Neovascularization (CNV) in Age-Related Macular Degeneration and in Diabetic Retinopathies [2, 3]. 2) the pattern of toxin exposure in the liver, and 3) the sequential segmentation of vertebrate somitogenesis [4, 5]. I will also discuss the types of questions that Virtual Tissue simulations can address and the types of experimental data required for their development and validation.