Mitochondrial dynamics are essential for maintaining organelle stability and function, and it is known that mitochondrial dysfunction is implicated in complex age-related neurodegenerative disorders including AD, PD and ALS [25-26]. The morphology of the mitochondrial network is in a constant state of flux, thereby retaining optimal populations of mitochondria. The transition between elongated reticular networks and punctate structures is dependent on two antagonistic processes, i.e. fission and fusion, both of which are vital for neuronal survival as they directly affect organelle number, shape and location [27]. In iPSC-derived neurons, grown on conventional unpatterned PDL/laminin-coated coverslips, the precise tracing of these events within individual neurons has been difficult to achieve, because neurite density varies dramatically due to uneven neuron growth (compare Figure 2B). Neurons grown on micropatterned surfaces extend their processes in a defined and uniform manner, which is dictated by the pattern design. This allows the precise evaluation of mitochondrial dynamics in individual neuronal processes in live neurons so that mitochondrial fission (Figure 3A, upper panel) or fusion (Figure 3A, lower panel) can be easily followed over time. To assess
