The brain is composed of billions of neurons that must connect with an appropriate set of targets to form the neuronal circuits that underlie its function. Inappropriate wiring of these neuronal connections leads to abnormalities affecting the sensory, motor and cognitive functions of the nervous system. During embryonic development, axons extend to their target in a highly directed manner by detecting a variety of attractive and repulsive molecular guidance cues presented by cells in the environment. We have recently found that a molecule called Sonic Hedgehog (Shh) guides growing axons. One of our goals is to identify the genes involved in axon guidance by Shh and characterize how they function to guide axons. In addition to helping us understand the immense complexity underlying the wiring of the nervous system, this work will help to identify novel strategies to promote the proper guidance and rewiring into neural circuits of regenerating axons damaged by neurodegenerative diseases, stroke, or brain and spinal cord injuries.