In order to study complex cellular interactions in the developing somite and nervous system, we have been refining techniques for labeling and imaging individual cells within the living vertebrate embryo. Most recently, we have been using MPLSM to analyze cellular behaviors, such as cell migration, filopodial extension, cell process collapse, and neuron pathfinding using time-lapse microscopy in 3-dimensions (3-d). To enhance the efficiency of two-photon excitation in these samples, we have been using a Zeiss LSM 510 NLO fiber delivery system with a Grating Dispersion Compensator (GDC). This system not only offers the convenience of fiber delivery for coupling our Ti:Sapphire laser to the microscope, but also affords us precise control over the pulsewidth of the mode- locked beam. In addition, we have developed a novel peptide/non-cationic lipid gene delivery system to introduce GFP plasmid into somite cells. This approach has allowed us to generate detailed 3-d images of somite cell morphologies at various stages of somite development in a way that best preserves the vitality of the cells being imaged.