The fragrance was introduced in the 1920s, and continues to sell at rates said to be one bottle per minute worldwide. Its popularity in the U.S. soared in the 1950s when Marilyn Monroe was asked what she wore to bed, and she replied "Why, Chanel No. 5, of course."
In terms of constituents, "its top notes include ylang ylang, neroli and aldehydes; its mid notes May rose and jasmine; and its base notes sandalwood, vetiver and vanilla." (an excellent example of how some things are poorly expressed in words).
But back to my original question. What ever happened to Chanel No. 4?
Coco Chanel commissioned the renowned perfumer Ernest Beaux to make six perfumes for her choosing. They were labeled No. 1, No. 2, etc. through No. 6... It was bottle No. 5 that was to Chanel's liking and became the chosen formula.Info and photo from Wikipedia.