The early studies of plant growth and development focused on embryogenesis. In the past twenty five years, it became possible to successfully analyze many more developmental processes, hence plant developmental biology became the generally accepted terminology. It refers to a multidisciplinary approach using expertise and tools from genetics, molecular biology and cell biology to study processes in development also beyond the formation of the embryo. Around that time, initiatives were taken to address biological questions in just a few model systems, such as Arabidopsis thaliana, Zea mays, Antirrhinum majus and Petunia hybrida, while the <<old>> model systems, i.e. potato, tobacco, used in regeneration and grafting experiments, were increasingly abandoned. International research programs were initiated in Arabidopsis at first to create stock centers and databases to proceed faster with the scientific research and to get deeper insight into plant biology. During the last five years the maize community made tremendous progress in developing tools and resources for their system. Milestones in plant developmental biology discussed relate to the molecular-genetic approach to study embryogenesis, autoregulation of meristems, leaf and flower initiation, leaf and flower formation and cell specification in the root. Developmental biology changed the research from descriptive to causal resulting in a number of genetic models. Future developments in research will focus on the study of a specific gene activity in a genome-wide context. The building of molecular networks will allow computer modeling of biological processes and its use for predictions and further experimentation. Sequence information derived from the multiple genome projects will be exploited in comparative biology.