These Americans are changing the world - and they're all under 40

Why she made the list: A "tech innovator who has worked on some of the most disruptive technologies, Singh is currently director for business development and part of a team that is forging new business for Microsoft in artificial intelligence and internet of things."

Why she made the list: Parcak is "an archaeologist who uses satellites to uncover hidden ancient treasures. She estimates we have excavated less than a thousandth of one percent of what is out there."

Why she made the list: "Born to Syrian and Palestinian immigrants in Tennessee, Ali served as a counterterrorism adviser as a White House Fellow under President Barack Obama and is currently an attorney at Bass Berry & Sims and director at Lodestone Advisory Group."

Why he made the list: Kass is "a food entrepreneur, policy advisor, and celebrated former White House Chef who is on a mission to reduce childhood obesity to just 5% by 2030."

Why he made the list: Socher is "one of the prodigies of the artificial intelligence and deep learning space whose breakthrough technologies are transforming natural language processing and computer vision."

Why he made the list: "An influential political commentator, Salam is the co-author of "Grand New Party" (2008) and a leading figure among reform conservatives, a movement dedicated to revitalizing the US right."

Why she made the list: Bergen "is the founder and executive director of Nest, a platform connecting local artisans with global consumers, helping them overcome supply chain hurdles with direct programming. She has been honored by the White House as one of the Top 100 Entrepreneurial Enterprises led by a young person."

Why she made the list: Kaliouby is "a pioneer of industry who's spearheading digital applications of emotion-sensing and facial coding."

Why she made the list: "Cofounder and portfolio manager of Matarin Capital, a hedge fund and equity asset manager for institutional investors, Gilbert is a recognized leader in a number of fields ranging from finance and economics, social justice and sustainability, to US foreign relations."

Why he made the list: "After establishing several successful nanotech and biopharma companies, Moradi is now the cofounder and CEO of Sensulin, a company that strives to provide a once-a-day solution for type I/II diabetics."

Why he made the list: "A New York based leader, Hudson is chief operating officer for the Credit Suisse Global Markets business and manages a diverse organization of more than 2,500 people. She is a champion and passionate voice for the professional advancement of women, particularly in financial services."

Why she made the list: Hill is "an innovator who is using business models to solve critical social and environmental challenges. She currently leads Apple's ambitious new Clean Energy Program converting the company's manufacturing worldwide to renewable energy."

Why she made the list: Lee is a "young and dynamic investor at Sequoia Capital" and a "former product manager at Google and CEO of Polyvore, a community-powered social commerce website whose mission is to empower people to feel good about their fashion style."

Why he made the list: Tomkins is a "private equity professional with a proven record of impact beyond the world of finance, helping leading families, foundations and endowments further their philanthropic impact."

Why she made the list: Loskota "works with government agencies to ensure more effective partnership with faith communities on public health and is involved several community groups, including NewGround: A Muslim-Jewish Partnership for Change."

Why he made the list: Henderson is "one of BCG’s strongest performing partners throughout his career, his focus is on economic and social development issues. A Chicago resident, he has worked on several initiatives in his city to improve its most disadvantaged neighbourhoods and enhance its relevance as a global city."

Why he made the list: Jain is "cofounder and CEO of Humin, a technology company that developed a platform for managing contacts and was bought by the dating-app, Tinder. He also founded the Kairos Society, an organization of young entrepreneurs working to create billion-dollar solutions to the world’s most significant challenges."

Why she made the list: Brown is "the youngest mayor to ever be elected in Compton, California, whose 'New Vision for Compton' is a revitalization strategy centered on 12 key principles that focus on family values, quality of life, economic development and infrastructural growth. She received the National Action Network Martin Luther King Award."

Why he made the list: Kinzinger is "a former armed forces pilot and Republican member of the U.S. House of Representatives who has emerged as a champion for improving the lives of veterans."

Why he made the list: Zhang is "one of the most acclaimed young scientists in the world and a pioneer of CRISPR, the breakthrough gene-editing technique that lets scientists manipulate the genetic code of organisms."