One of the major goals of developmental neurobiology is to examine how complex neural circuits form and to understand the mechanisms directing precise spatial and temporal growth in these circuits. One important question within this broader field to be addressed is: How do structures containing multiple neurons fasciculate? To achieve this, and as a test case, I propose to investigate the development and growth of the C. elegans lateral nerve cord (which comprises CAN, ALA and BDU neurons and the excretory canal cell) in live embryos. First I will employ light sheet microscopy paired with cell-specific promoters to investigate the migration and outgrowth of lateral nerve cord neurons during embryogenesis. Volumetric images of the embryo will be untwisted using software developed by the Shroff lab to monitor the positions of the lateral nerve cord cells over time. Subsequently, photoablation will be used to kill individual cells and investigate the impact of cell ablation on the lateral nerve cord development and order. Based on the timing and position of the observed migration and outgrowth events, and impact of cell ablation, I will build a 4D map that describes the contribution of each cell to the development of the lateral nerve cord as a whole.