Starting with an accidental observation, it took us 20 years to convince the scientific community that we had identified a new signal transduction pathway involving some 250 proteins. Time will tell the true significance of this pathway. For now, we have been able to find it a role in axon guidance, in cellular migration and in the physiological plasticity of the cerebral cortex.This discovery of the intercellular movement of transcription factors, which went against certain dogmas, was per...