PepsiCo chief executive Indra Nooyi, one of the most prominent female CEOs in the world, announced Monday she will step down after leading the giant soft drink company for 12 years. Nooyi, 62, has worked at PepsiCo for 24 years. In a tweet, she expressed "mixed emotions" about leaving her position and said she "never imaged" she'd have the opportunity to lead "such an extraordinary company." PepsiCo's current president, Ramon Laguarta, will take over as CEO in October. Nooyi will remain as chairman of the board until early next year.Nooyi, who was born in India, is a rarity on Wall Street — a woman and a minority leading a Fortune 500 company. Among the 500 companies in the S&P 500, only 25 — 5 percent — are led by women. Nooyi's departure leaves only one woman of color among the Fortune 500 CEOs.Nooyi told Bloomberg News on Monday that she planned to advocate for more women to serve at the highest levels of corporations."My job is, in fact, just beginning once I leave PepsiCo because I can do things now that I was constrained to do when I was CEO of the company," she said.While at PepsiCo, Nooyi faced a challenging time shifting consumer tastes toward more healthy snacks. She helped the company expand its healthier options, including Baked Lay's potato chips and Naked juices. PepsiCo still sells sugary sodas and less healthy snack options. PepsiCo's products include snacks under the Frito-Lay banner such as Dorito corn chips, and carbonated drinks such as Pepsi and Mountain Dew. Other well-known brands include Tropicana, Gatorade and Quaker Oats. Nooyi began her corporate career in India before attending the Yale School of Management.Under her leadership at PepsiCo, the company's net revenues rose from $35 billion in 2006 to $63.5 billion in 2017, with much of the growth coming from international markets.Nooyi tweeted words of praise about her successor.