Neurons are highly polarized cells with two molecularly and functionally distinct domains that emerge from the cell body: a single thin, long axon that transmits signals, and multiple shorter dendrites that are specialized to receive signals. The ability of neurons to polarize is crucial for synaptic transmission, and knowledge of the mechanisms that govern neuronal polarization is fundamental to our understanding of normal neural development, plasticity as well as neuropsychiatric diseases. Mouse primary and human iPSC-derived neurons from genetic models of neurodegenerative diseases have been used to study disease-associated changes of neuronal organization or network formation, primarily focusing on neurite outgrowth phenotypes [36-37]. Further, high throughput screening studies for human neurons have been developed to assess phenotypic outcomes including neurite outgrowth and branching [38]. However, it remains very challenging to reliably examine these processes in iPSC-derived neurons under conventional culture conditions due to aforementioned clustering of cells. To study outgrowth as an early process in the formation of neuronal networks, we imaged iPSC-derived neurons 50 hours after plating onto a substrate patterned with an array of flower-shaped features (Supplemental Movie
