Helen Gurley Brown, the former Editor-In-Chief of Cosmopolitan magazine, has died today.

Brown, who was considered a "true pioneer in journalism," died at New York-Presbyterian/Columbia University Medical Center in New York City. The cause of her death was not disclosed. She was 90 years old.

"Helen Gurley Brown was an icon. Her formula for honest and straightforward advice about relationships, career and beauty revolutionized the magazine industry," said Frank A. Bennack, Jr., CEO of Hearst Corporation, publisher of the monthly women's magazine.

"She lived every day of her life to the fullest and will always be remembered as the quintessential 'Cosmo girl.' She will be greatly missed," he added.

Brown joined Cosmopolitan magazine in 1965, 3 years after she published her controversial book, "Sex and The Single Girl." She edited the magazine for thirty-two years before her retirement.

Under Brown's helm the magazine quickly turned around from declining sales. She created the formula the publication uses today to maintain sales and popularity: featuring unclothed men inside; celebrities and models on the cover minimally dressed in bikinis, shorts and mini-skirts with multiple cover lines about sex, telling readers various ways on "how to please your man."

Her book, "Sex and the Single Girl," topped bestseller lists in its first year but was deemed controversial by critics for encouraging women to enjoy sex whether they were married or not. Brown has been credited for helping revolutionize sexual freedom in the 1960s.

Cosmopolitan magazine was first published in 1886. When Brown started working there, it became a young women's magazine focusing on sex, career, fashion, beauty and relationships and has maintained that editorial direction ever since.

View the gallery of some of today's hottest stars who have appeared on the cover in recent years.