For animals, it is vitally important to time and synchronise development and physiological activity of the different body systems and to adjust behaviour accordingly. The timing and synchronisation of different body systems and behaviour requires both a timer (represented by central and peripheral endogenous clocks) and an integrating communication system (represented by the (neuro)endocrine system). Yet, we know astonishingly little about the complex neuronal and endocrine pathways and underlying molecular and cellular signalling mechanisms by which endogenous clocks and neuroendocrine systems interact with each other. Such knowledge could provide a handle to understand and treat associated developmental disorders and circadian dysfunctions including impaired fertility, sleep disturbances and psychiatric problems that can result from long-term disruption of this integrated timing. The aim of this project is to dissect the interactions between developmental and circadian timers and the neuroendocrine system, and to start characterising cellular and molecular signalling principles underlying timed behaviour. A main focus here is on the interplay between peptide and steroid hormone signalling and its circadian control. We also aim to find out where in the brain circadian and developmental signals are integrated to time a specific behaviour. This specific behaviour will be the eclosion of the fruit fly Drosophila. The fruit fly appears a highly suited model system for this project as it is genetically and experimentally well tractable, and possesses a relatively low number of individually identifiable neurons. This in the long range offers the possibility to in completeness decipher neuronal and hormonal connections between central and peripheral clocks and target tissues from the molecular to the systemic level. Eclosion is well suited as it is timed by developmental and circadian timers, and its timing is under control of both peptide and steroid hormones. From a zoological point of view, understanding the architecture of the neuronal-endocrine network timing eclosion is of great interest since correct eclosion timing is most critical for the survival and fitness of insects and other arthropods, which represent the vast majority of animals on our planet.