The subdivision of the vertebrate embryo into repeating segments called somites, from which the muscles and bones will grow, is one of the oldest problems in developmental biology, recognized by Malpighi in the 1600s. This proposal focuses on the composition, function and dynamics of a population of genetic oscillators (termed the segmentation clock) that couples the spatial elongation of the embryo with the serial formation of somites. The research proposal outlines molecular, cellular, embryological and biophysical approaches to understanding these complex temporal and spatial phenomena in the zebrafish embryo. The work delves into three main areas: identification of oscillator components, control of oscillator frequency, and coordination of the oscillations in space and time. Novel methods and technologies to measure spatial growth rates, genetic oscillations, and signaling events in real-time in the growing embryo are proposed. Mathematical simulation and analytic physical theory to describe both morphological dynamics and microscopic biochemical mechanisms are to be developed in parallel with the biological experiments. The application of theory and experiment to the segmentation clock will give a unified framework in which to make and test physical theories of collective processes and their precision and robustness in developing systems. Coordination of the field of cells that gives rise to somites by synchronized genetic oscillations is a novel paradigm for patterning tissues, raising the possibility that genetic oscillations may be widely used in embryonic patterning, differentiation and morphogenesis. Analysis of the segmentation clock should provide the key concepts and methods to explore such systems.