Structure and function of the growth cone in axon navigation. (a) The growth cone that tips the axon is a highly motile structure composed of a microtubule-rich central domain and an actin-rich peripheral domain, forming lamellipodia and filopodia. During axon navigation, the growth cone explores its environment by extending and retracting its filopodia. (b) The axon trajectory is defined by environmental cues which exert attractive (in green) and repulsive (in red) effects on the growth cone. (c) Axons from different neuron types (here in blue, pink, and green) express specific combinations of receptors and thus respond differently to the same cues present in their environment and thus navigating distinct pathways.