The "Proust Phenomenon"

Most everyone has had the occasion of breathing in an odor and suddenly finding themselves lost in the reverie of a memory from long ago; the smell of fresh baked bread perhaps bringing back mornings at Grandma’s house or a certain perfume that always brings back a certain time in high school. Such odor/memory links are known as the "Proust Phenomenon" in honor of Marcel Proust, the French writer who romanticized the memories evoked by the smell of a madeleine biscuit after soaking in tea, in his novel, À la recherche du temps perdu.

In Search of Lost Time or Remembrance of Things Past (French: À la recherche du temps perdu) is a novel in seven volumes by Marcel Proust. His most prominent work, it is popularly known for its considerable length and the notion of involuntary memory, the most famous example being the "episode of the madeleine."
The role of memory is central to the novel, introduced with the famous madeleine episode in the first section of the novel and in the last volume, Time Regained, a flashback similar to that caused by the madeleine is the beginning of the resolution of the story. Throughout the work many similar instances of involuntary memory, triggered by sensory experiences such as sights, sounds and smells conjure important memories for the narrator and sometimes return attention to an earlier episode of the novel. Although Proust wrote contemporaneously with Sigmund Freud, with there being many points of similarity between their thought on the structures and mechanisms of the human mind, neither author read the other.
The madeleine episode reads:

No sooner had the warm liquid mixed with the crumbs touched my palate than a shudder ran through me and I stopped, intent upon the extraordinary thing that was happening to me. An exquisite pleasure had invaded my senses, something isolated, detached, with no suggestion of its origin. And at once the vicissitudes of life had become indifferent to me, its disasters innocuous, its brevity illusory – this new sensation having had on me the effect which love has of filling me with a precious essence; or rather this essence was not in me it was me. ... Whence did it come? What did it mean? How could I seize and apprehend it? ... And suddenly the memory revealed itself. The taste was that of the little piece of madeleine which on Sunday mornings at Combray (because on those mornings I did not go out before mass), when I went to say good morning to her in her bedroom, my aunt Léonie used to give me, dipping it first in her own cup of tea or tisane. The sight of the little madeleine had recalled nothing to my mind before I tasted it. And all from my cup of tea.

Valentin Louis Georges Eugène Marcel Proust (1871 –1922) was a French novelist, critic, and essayist best known for his monumental À la recherche du temps perdu (In Search of Lost Time; earlier translated as Remembrance of Things Past). It was published in seven parts between 1913 and 1927.
Proust's father, Achille Adrien Proust, was a prominent pathologist and epidemiologist, responsible for studying and attempting to remedy the causes and movements of cholera through Europe and Asia; he was the author of many articles and books on medicine and hygiene. Proust's mother, Jeanne Clémence Weil, was the daughter of a rich and cultured Jewish family from Alsace. She was literate and well-read; her letters demonstrate a well-developed sense of humour, and her command of English was sufficient for her to provide the necessary assistance to her son's later attempts to translate John Ruskin.
Proust had a close relationship with his mother. To appease his father, who insisted that he pursue a career, Proust obtained a volunteer position at the Bibliothèque Mazarine in the summer of 1896. After exerting considerable effort, he obtained a sick leave that extended for several years until he was considered to have resigned. He never worked at his job, and he did not move from his parents' apartment until after both were dead.
Proust, who was a closeted homosexual, was one of the first European novelists to mention homosexuality openly and at length in the parts of À la recherche du temps perdu which deal with the Baron de Charlus.
His life and family circle changed considerably between 1900 and 1905. In February 1903, Proust's brother Robert married and left the family home. His father died in November of the same year. Finally, and most crushingly, Proust's beloved mother died in September 1905. She left him a considerable inheritance. His health throughout this period continued to deteriorate.
Proust spent the last three years of his life mostly confined to his cork-lined bedroom, sleeping during the day and working at night to complete his novel. He died of pneumonia and a pulmonary abscess in 1922.