I investigate, how during a critical period towards the end of embryogenesis, fundamental properties of neurons and neuronal circuits are determined, to specify homeostatic setpoints. To address this, I am taking advantage of the well characterised Drosophila larval locomotor network, which also has a clearly defined critical period, coincident with the transition from spontaneous unpatterned to coordinated activity. My aim is to identify cellular and molecular substrates which together define the homeostatic setpoint of the locomotor circuitry. Specifically, I am focusing on the role of calcium in this process. In neurons, calcium serves a dual function; as charge carrier and intracellular messenger, giving it the potential to decode neuronal activity during the critical period into mechanisms that are essential for establishing homeostatic setpoints. Thus, calcium dependent adjustments during the critical period can range from tuning of single cells to network wide modifications.