The goal of this symposium is to promote interactions between researchers studying neural circuits both in traditional model systems (worm, fly, fish, mouse), in humans, and in diverse, emerging models to (i) discuss the origins, commonalities and differences of animal nervous systems, (ii) highlight the spectacular capabilities of neural circuits to control animal behaviour, and (iii) reflect on how technological innovations will open up new possibilities to understand and repair the nervous system. By bringing together a unique and eclectic mix of scientists studying nervous systems from the molecular to the psychological level, this symposium should stimulate novel cross-fertilisation of ideas and methodologies to understand neural circuit structure and function.