"The Interpretation of Dreams" (1899) by Sigmund Freud is a pioneering work that introduces his theory that dreams are a manifestation of unconscious desires and repressed thoughts. Freud argues that dreams are a form of wish-fulfillment, revealing hidden emotions and unresolved conflicts from the unconscious mind. He distinguishes between the manifest content (the literal storyline of the dream) and the latent content (the hidden, symbolic meaning), suggesting that dreams use mechanisms like condensation, displacement, and symbolism to disguise these desires. This work is considered foundational in the field of psychoanalysis, offering a new method for exploring the unconscious.