Following in the footsteps of other noteworthy people who have been named Time's "Person of the Year" — like Pope Francis, Winston Churchill and Mahatma Gandhi — is 16-year-old Swede, Greta Thunberg. Thunberg is known for her environmental activism, which started when she began protesting outside the Swedish Parliament. Her "Fridays for Future" movement calls on other students her age (and younger) to engage in strikes against governments around the world as a way of speaking up on matters of climate change.

Nick Lowinger was just 5 years old when he visited a homeless shelter with his mom and recognized that many of its children didn't have adequate footwear. Some were even sharing a single pair of shoes between siblings. Seven years later, he donated his first pair of sneakers and laid the groundwork for what would become the Gotta Have Sole Foundation, which has donated nearly 100,000 pairs of shoes to homeless shelters to date. Today, he has partnerships with retailers from AT&T to Zappos.

Malala Yousafzai is best known only by her first name, a la Madonna, and is celebrated for her advocacy in helping women and children pursue education. Malala was 15 years old when she was shot on her way to school by members of the Taliban in her native Pakistan, in retaliation for her activism. That incident did not slow her efforts, however. At 17, she was the youngest ever to be awarded the Nobel Prize and in 2013, she released a book that went on to become an international bestseller. Her work continues through her foundation, The Malala Fund.

The water crisis in Flint, Michigan, has been ongoing since 2014 when Mari Copeny was just 6 years old. Two years later, at age 8, she penned a letter to then-President Barack Obama in an attempt to compel him to engage in serious talks with lobbyists and political leaders. Since then, she has been hard at work raising funds, donating school supplies and backpacks, and gathering toys for Flint youth, partly through her Pack Your Back program, while also keeping the water crisis in the public eye.

Sophie Cruz was 5 years old when she traveled to Washington, D.C., to meet with Pope Francis and garner his support for the Deferred Action for Parents of Americans Act. She ran out into the street toward the Pope's motorcade, but security turned her away. It didn't stop Pope Francis from noticing the girl and reaching out to her, ultimately speaking on the issue with Congress. Cruz later met with President Barack Obama and also participated in the Women's March in D.C., serving as its keynote speaker.

In 2013, Chicago made plans to shut down upward of 50 public schools, but not without pushback from an unlikely source, a Marcus Garvey Elementary School student named Asean Johnson. Johnson spoke out against the mayor and also spoke at the “Realize The Dream” rally, where he called on leaders to provide equal funding and resources for all schools. Johnson kept his own elementary school's doors open and has plans to run for mayor of his town in 2025, when he'll be 21.

At 16, most young men are playing video games and hanging out with friends. When Jack Andraka was 16, he was looking for inexpensive detection methods for pancreatic cancer. Fueled by the loss of a close family friend, Andraka developed his screening method using a small dipstick probe that analyzes a minute blood sample in just five minutes. The discovery earned Andraka the support of at least one researcher and helped him grab both the Smithsonian American Ingenuity Award and the grand prize at the Intel International Science and Engineering Fair.

Now 19, the environmental activist already has a lengthy list of accomplishments in helping world leaders understand more about climate change. He has spoken at the United Nations multiple times and is named as a plaintiff in a federal lawsuit alleging that the government has failed to properly address climate change issues. Today, he is youth director for the conservation group, Earth Guardians, and also uses the power of music to help illustrate his message.

Anoyara Khatun understands child trafficking because she endured it when she was just 12 years old. After being rescued by Save the Children, Khatun turned her testimony into triumph in her native West Bengal, India. Khatun has received the Nari Shakti Puraskhar (Women Power Award) for her work with a network of children's groups in 80 villages with Save the Children. Through her work, she has helped save hundreds of children from enduring the same experiences she had.

Who would have thought that lemonade could be so powerful? Alex Scott was 4 years old when she hosted her first lemonade-stand-turned-childhood-cancer-fundraiser in her front yard. Scott battled childhood cancer and wanted to help others like herself. The lemonade stand became an annual occurrence in the Scott household and has since sparked similar lemonade stand fundraisers across the country. Alex died in 2004 at the age of 8, but her legacy of giving continues. To date, more than $150 million has been raised to find a cure for childhood cancer.

In 2013, Ann Makosinski invented a flashlight using an alternative energy source – in this case, body heat. The Hollow Light helped propel Makosinski to the forefront of the alternative energy discussion while delivering light to those who can't afford electricity and reducing waste in landfills around the world. The flashlight, which won the Google Science Fair in 2013, uses only the heat from the human hand. She also invented the eDrink mug, which can charge a cellphone using the heat from a beverage.

In 2011, Easton LaChappelle turned his Legos into a prototype for a prosthetic hand. The invention eventually shifted from a hand to an arm, the RoboArm. But it wasn't until LaChappelle met a young girl at a science fair (her prosthetic arm cost $80,000) that the goal of his work became more clear, to make prosthetics more affordable for those who need them. LaChappelle's 3D-printed prosthetics carry a price tag in the hundreds, not the thousands, and his scientific mind has prompted some to call him the next Elon Musk.

Many people begin wearing glasses at a young age; for Yash Gupta, that was at 5 years old. At 14, after breaking a pair and waiting for a replacement, Gupta became inspired to help others who needed eyeglasses but couldn't them. His Sight Learning organization, to date, has donated $1.5 million worth of eyewear to students in places like Honduras, Haiti and India. Gupta turned his appreciation for clear sight into a mission to provide that fundamental right to others.

In a world that places a premium on perfect bodies and faces, Julia Bluhm waged war against Photoshop and won. At the age of 14, in 2012, she successfully campaigned for the teen magazine, Seventeen, to celebrate real girls and real bodies by disavowing the use of Photoshop in its imagery. Today, Bluhm continues her crusade for body positivity and confidence through work with Spark Movement, where she says, "I’ve been a feminist ever since I knew what a feminist was."

Boyan Slat was diving during a fishing trip in Greece when he discovered a problem — plastic pollution taking over the oceans. Just 16 at the time, Slat began working on developing Ocean Cleanup, a non-profit dedicated to protecting the world's water. The goal of the organization, which has raised more than $32 million, is to find solutions to rid the world's oceans of plastic. His TEDx talk on a revolutionary cleanup system utilizing the ocean's currents went viral – at the ripe old age of 17.

Third-grader Katie Stagliano's start to improving the world around her began with a 40-pound cabbage. She donated it to a local soup kitchen, and that gift fed nearly 300 people. It prompted the now-20-year-old to create Katie's Krops, a youth gardening movement that encourages kids of all ages to grow – and donate – crops from vegetable gardens. In 2018, nearly 40,000 pounds of vegetables were donated nationwide to hunger relief programs and families in need.

Jaylen Arnold was already battling Tourette's Syndrome, Asperger's and OCD, so it didn't seem fair when his peers added more for him to deal with by bullying him for his differences. Arnold turned those lemons into lemonade, though, creating the Jaylen Challenge Foundation. Through the foundation, he has addressed more than 100,000 children with his "Bullying No Way!" message. Arnold takes his message to "kids that bully other kids, especially disabled ones," in an effort to stop all bullying.

Do you think you can't make a difference? Tell that to Ryan Hickman, who developed a passion for recycling when he was 3 years old. Four years later, he started a program he called Ryan's Recycling, gathering plastic, paper, bottles and cans not only from family and neighbors, but all across his native Orange County, California. Today, at 10 years old, he spends time every week sorting recyclables and preparing them to take to a local recycling center. According to his website, more than 107,000 pounds have been recycled thanks to his efforts.

In 2007, then 16-year-old Thandiwe Chama received the International Children's Peace Prize, but her work began long before that. When Chama's school in Zambia closed, she led a march of 60 students to another area school – at the age of 8. Chama said, "We cannot achieve sustainable development without ensuring that my rights, my education and my health is just as important as that of my brothers." Today, she works as an education rights activist in her home country and has authored a book titled "‘The Chicken with AIDS."

There's nothing quite like New England winters, a fact Cassandra Lin knew all too well. As a Rhode Island fifth grader, she discovered that basic cooking oil could be recycled and turned into biofuel to help people heat their homes. She founded Project TGIF (Turn Grease Into Fuel), collecting more than 4,000 gallons of grease every month and turning it into biodiesel to help families in need. Lin has been able to get more than 100 area restaurants to participate, providing assistance to families and offsetting carbon dioxide in the atmosphere.

It can be tough to enjoy reading if you can't identify with any of the characters, which was precisely the problem Marley Dias was having. Dias started the #1000BlackGirlBooks hashtag to collect 1,000 books with black female protagonists. Those books could then be donated to girls just like her. Dias was only 10 years old when her initiative began. To date, more than 11,000 books have been donated, and Dias has authored a book titled "Marley Dias Gets It Done: And So Can You!"

Mary Grace Henry turned a passion for sewing into a world-changing initiative at the age of 12. Henry had the idea to create and sell reversible headbands and use the funds to help send an underprivileged girl to school. Achieving her initial objective wasn't enough, however. Henry created the charity, Reverse The Course, continuing her headbands for education mission, which has helped nearly 200 girls in Kenya, Uganda, Paraguay and Haiti.

Kelvin Doe is one of Sierra Leone's – and Africa's – most famous inventors. He got his start with spare parts and scrap metal. Doe started at the age of 11, using bits of leftover parts to help find a solution for electrical outages in his community. By 13, he had come up with a battery capable of powering multiple neighborhood homes. That same year, he combined the right pieces to develop his own community radio station, where he is known as DJ Focus. His entrepreneurial mind has earned him meetings with multiple world leaders and a spot in MIT's "Visiting Practitioner's Program."

Melati and Isabel Wijsen were 10 and 12 years old in 2008 when they were inspired by Rwanda's ban on plastic bags. They envisioned something similar in their native Bali. Indonesia has historically been one of the largest plastics polluters in the world. Now, thanks to the Wijsen's initiatives, including beach cleanups and a petition aimed at getting their government's attention, Bali is (plastic) bag-free, with Indonesia as a whole to soon follow suit.

Named one of "Africa's most influential women" by Forbes Magazine, 17-year-old Zuriel Oduwole already wears many titles – self-taught filmmaker and education advocate among them. Oduwole has interviewed three dozen world leaders and created nearly 10 documentaries aimed at promoting the importance of education among young women in her native Africa. Founder of "Dream Up, Speak Up, Stand Up," Oduwole seeks to encourage African girls to pursue their education.