The libido key for sexual activity fuel of psychic energy, regulated by sex hormones and neurotransmitters. Hypoactive sexual desire disorder, affects 10% or 6 million premenopausal women in USA. Freud: libido, energy found in the Id, the unconscious structure of the psyche, has phases in toddlers: Oral stage, Anal stage, Phallic stage, Genital stage in adults. Jung: libido is the totality of psychic energy. Psychological factors reduce the desire for sex: lack of privacy, stress , depression, sexual abuse. Posttraumatic Stress Disorder: decreased brain activity in areas of emotion. Libido is affected by hypothyroidism, medications, attractiveness of one's partner, contraception in women. Erection induced by environment. Freud: The iceberg metaphor relates Ego, Id, Superego with conscious and unconscious mind. Libido drives: Eros and Thanatos. Eroticism: humans experience sex, key in hominization. Electromagnetic waves with brain stimulation change the sex drive libido. Psychoanalysis: tool in life. Consciousness is self in space-time. First appearing in the Mayans and Incans. Developmental psychologist: Stages of cognitive and moral quality.