Jacques Lacan
Jacques Lacan was a french psychologist born in Paris on 1901, and died in the same city on 1981. Very influenced by psychoanalysis of Sigmund Freud, driving a return to their ideas and discarding the post-Freudian psychoanalysis, that was more biologist. He studied medicine on university and got a specialization on psychiatry.
He included to the psychology analysis concepts of existentialist philosophy, anthropology, maths and essentially linguistic, that improved the way of understand the unconscious, analyzing how an structural form of language based in metaphors and symbols. other important idea of him is the relevance of "the others" on the own personalty and on the image that we formed of ourselves.
One of his theories that i like is called mirror stage, that explain how we formed our "ego" based on a image of other person in childhood. Also we are influenced for the other in the rest of our life, because the social bond is still important for the constitution of the self.
there are more important theories of Lacan, but it should be very hard to explain all of them, but with this information you can know something about his ideas. I hope that you liked this.