She is one of the biggest stars in Silicon Valley, but multimillionaire chief executive Marissa Mayer has her hands full trying to revive the fortunes of faded Internet pioneer Yahoo.

The 40-year-old, who once worked at a grocery store, is listed as the 22nd most powerful woman by Forbes magazine.

She is also among the best-paid executives, with a package worth $42 million last year including stock options.

But Mayer faces a major test with Yahoo set to spin off its core operations into a separate company that will allow investors to more clearly see its value without the distortion from its huge investment in China's Alibaba.

She is not the first CEO seeking to reinvent Yahoo, but she had initially inspired confidence with her experience as a manager at rival Google.

At Google, Mayer was responsible for local and geographical products including Google Maps, Google Earth, Street View and local search for desktop and mobile.

She joined Google in 1999 as its 20th employee and led efforts for many of Google's most recognizable products, including the development of its flagship search product and homepage.

At Yahoo, where she became chief executive in 2012, she went on a buying spree that included a $1 billion acquisition of the blogging platform Tumblr to reach a younger audience.

She coined the term MAVENS in outlining her strategy but the term is hard to grasp outside the geek world: it emphasized "mobile" products as well as "video," with "native" advertising -- ads integrated into other services -- and "social."

These segments of the business have been growing, but Yahoo's overall performance has been uneven, leaving its investors unsettled.

Born in a small Wisconsin city, she worked at a grocery store before attending Stanford University, where she studied computer science.

While her intellectual skills qualify her as a nerd, her good looks and star quality have put her on the cover of magazines including Fortune, Vanity Fair and Vogue, which showed pictures of her in a fashion spread.

Glamour magazine named her "woman of the year" in 2009 and she has been on several lists of influential tech personalities.

Married to financier Zachary Bogue, Mayer has also been under scrutiny for how she handles gender issues in the workplace.

She boosted maternity leave at Yahoo to 16 weeks but only took two for the birth of her first child in 2012 -- drawing plaudits and critics.

She recently announced she was pregnant with twins and would be taking "limited time away and working throughout."