In this note I have limited myself to describing some convergent and divergent developments arising from the innovative concepts present in The Ego and the Id. It could be argued that a part of the psychoanalytic movement wished to emphasize the function of the Ego (Anna Freud, Hartmann, Rapaport), while another part (Melanie Klein and her followers) delved into the dynamics of the Superego and the Id in primitive and pathological states of mind. I will examine three themes presents in The Ego and the Id: the assertion that a part of the Ego is unconscious; the idea that the death drive becomes part of the dynamics of melancholia and its Superego; the concept of fusion and defusion of the life and death instinct. Freud's writing represents a forge of new ideas that have made psychoanalysis ever more creative and capable of understanding the complexity and mysteriousness of the human mind.