A complete understanding of biological evolution requires from us to uncover the mechanisms that control embryonic development, including their variations among phyla. In the last 25 years, the work of developmental biologists has been almost completely dominated by a molecular outlook, in which the identification of "developmental genes" in a few model organisms has been of key importance. As a result, we now know a lot about the molecular level of embryonic development in these few organisms but, unfortunately, we know much less about the other two equally important levels at which development unfolds: the cell-behavioral level (what embryonic cells actually do during development), and the morphological level (the actual changes in shape and form that occur in embryonic cells and groups of cells). Additionally, the strong focus on model organisms has made the development of analytical tools that work across species more difficult, hampering comparative analyses of embryonic development. Along with colleagues at the Salk Institute, I have proposed a general framework for an integrative research program in Developmental Biology, based on what we call the "minimum developmental set" (MDS) concept. We have proposed that it is possible to describe embryonic development using a finite number of carefully chosen "descriptors" that define the molecular, cell-behavioral, and morphological levels of embryonic development, making possible their display in bioinformatics frameworks (or "maps") that make correlation studies between molecular, cell-behavioral, and morphological data sets easier to visualize and understand. This project has three specific aims. First, to continue with the conceptual development of the MDS framework, especially regarding its relevance to the analysis of the evolution of developmental mechanisms. Second, to demonstrate the feasibility of elaborating, studying and defining a "minimum cell-behavioral set" for a well-studied embryonic structure, the developing vertebrate limb bud (and possibly show that the MDS method can also be applied to non-model organisms). Third, to explore the kind of information that can be obtained by comparing "minimum molecular maps" and "minimum cell-behavioral maps" in the wild-type limb bud and in limb buds in which specific changes in cell behaviors and in morphology have been induced through local exposure to morphogens. These conceptual and experimental activities have the potential to constitute a proof-of-principle for a far-reaching new integrative approach to evolutionary and developmental studies.