By studying the action of drugs on the brain, scientists gain insight into the workings of human consciousness. Drugs act on our brain, disrupting its communication circuits - a gigantic network of one hundred billion neurons, which science, for the past fifteen years, has known better and better. Beyond the effects of drugs, it is the process of addiction that is at the heart of the studies. Neurobiologists, geneticists, psychiatrists, pharmacologists and, increasingly, psychoanalysts, are bringing their positions closer together. This documentary series takes stock of the progress of their common knowledge.