Fruitflies only have around 80.000 neurons (compare this to around 20.000.000.000 neurons in our brain), but nearly as many neuropeptides as humans or other mammals. Neuropeptides are key factors that modulate (fine-tune) small neuronal circuits to perform astonishingly complex tasks and integrations. As hormones, peptides also serve as the chemical information channel between peripheral tissues and the brain. My research focusses on the characterisation of the chemical and cellular structure and function of peptidergic systems in the fruitfly, Drosophila melanogaster. The underlying aim is to understand how the small insect nervous system and the central clock in the brain regulates the activity of peptidergic neurons and the release of peptide hormones within a physiological and behavioural framework. The answers will help us to understand the evolution of peptidergic signaling and its circadian regulation, its significance for the astonishing performance of mini-brains, and the unmatched adaptive flexibility of the most diverse animal group on our planet.