Neurons, and the networks in which they exist, function within a physiologically appropriate activity range, often referred to as ‘homeostatic set-point’. During development, after much of the network architecture and basic connectivity has been established, a temporally restricted phase of heightened plasticity sets in, referred to as the Critical Period, during which this activity set-point is specified. Critical period experience, including the temperature that embryos are exposed to, nerve cell activity or levels of reactive oxygen species experienced, all provoke differential set-point adjustments in response. This occurs both at the single cell level, as well as across the network. I am exploring how critical period experience is translated into lasting adjustment at single cell level, focusing upon the morphology, connectivity and physiology of a model synaptic terminal, the Drosophila neuromuscular junction in the larva. We have begun a transcriptomic analysis to explore critical period-induced changes in gene expression that will ultimately underpin the change in cellular properties that we see (e.g. as measured by imaging, electrophysiology and behavioural analysis).