How neural circuits assemble during development influences functional adult circuit architecture, specificity, and variability. Live observation of brain development reveals stochastic and dynamic processes that help to understand functional constraints in the adult circuitry. In the first part of this chapter, we will explore what live imaging tells us about how dynamic processes create and constrain circuit specificity. In the second part of this chapter, we provide a current view of how live observation can be achieved in intact Drosophila brains in comparison to developmental imaging in other species. The goal of this chapter is to provide both the context and tools to understand neural circuits as a function of their developmental context.