Noa Mintz started her first business in 2008, running art classes for kids during the summer for a small fee. Two years later, she founded a children’s party planning business. To make sure her staff was following workplace protocol, she wrote an employee handbook for guidance.

As she looks back on her ventures six years later, Mintz is not impressed.

“Since I was, after all, under the age of 10, the execution wasn’t perfect,” she says.

Today, the 16-year-old entrepreneur runs a full-service childcare agency in New York City called Nannies by Noa, that matches nannies with families in need of a caregiver. She vets candidates, handles customer service, and ensures background checks are conducted on each nanny.

When she started high school two years ago and needed more time for schoolwork, Mintz hired a full-time CEO with 25 years of industry experience. She has since hired two additional associates.

“The best part by far is the fact that I am a job creator and have been able to get so many people employed,” Mintz says. “It is rewarding and empowering.” Mintz says she has found nannies for hundreds of families in the New York area, and the primary referral source for her business is word of mouth.

Mintz is on Fortune’s list of the 18 most innovative and ambitious teens under 18 years old. Some of these young entrepreneurs are inventing new products, building brands and making millions. Most haven’t even graduated from high school, which means the teens profiled below will have plenty of time to stake their claim on Fortune’s annual 40 Under 40 list.

The responses below have been edited for clarity and length.

1. Noa Mintz, founder of Nannies by Noa

noa-1-of-1 Photo: Alexandra Wolf

Age: 16
The business: Nannies by Noa is a full-service childcare agency, serving families in New York City and the Hamptons.
In 20 years, I will be … “In a business that places a premium on customer service. I anticipate I will be working on a venture that was triggered by a problem and created from a solution — and that may be Nannies by Noa, which is only four years old.”
Best advice I’ve ever received: “From my middle school principal: ‘Early is on time, on time is late, and late is unacceptable.’”

2. George Matus, founder of Teal

georgematus Courtesy George Matus

Age: 18
The business: Teal sells commercial drones, and its first product is a battery-operated, camera-equipped unmanned aerial vehicle that reaches speeds of 70 mph. Matus has raised $2.8 million in seed funding and is a Thiel Fellow.
In 20 years, I will be … “Involved in leading edge technologies and at the forefront of their creation. And hopefully, in 20 years, I’ll be able to own a Tesla, too.”
Best advice I’ve ever received: “When I was really little, my parents kept telling me to find what I love.”

Related: This Teenage Entrepreneur Raised $2.8 Million for His Drone Startup In-Between High School Classes

3. Mikaila Ulmer, founder and CEO of Me & the Bees Lemonade

US-POLITICS-WOMEN-OBAMA Photo: Saul Loeb/AFP/Getty Images

Age: 11
The business: Me & the Bees sells lemonade that uses flaxseed and local honey as a sweetener, and can be found in retailers like Whole Foods and Wegmans. A portion of the profits go to organizations dedicated to save honeybees from extinction.
In 20 years, I will be … “A social entrepreneur. I want to have graduated from college and continue teaching families and kids about entrepreneurship. Hopefully by then, I would have saved the bees and found a new problem to solve.”
Best advice I’ve ever received: “From my parents: they always tell me to dream big and that I can do anything I want, so I translated that into ‘Beelieve.’”

4. Mihir Garimella, creator of Firefly

mihir-garimella-headshot Courtesy Mihir Garimella

Age: 17
The business: Firefly is a low-cost, intelligent drone for first-responders that can enter and explore dangerous environments to find people who are trapped.
In 20 years, I will be … “Leading ambitious, high-impact research projects and trying to bring them to the market. My future is still pretty open, and I’m not sure exactly what I’ll work on, but I do know that I want to use computer science and robotics to make a difference.”
Best advice I’ve ever received: “Dig into problems that I see or experience.”

5. Moziah “Mo” Bridges, founder of Mo’s Bows

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Photo: Annabella Charles Photography

Age: 14
The business: Mo’s Bows offers colorful, handmade ties and men’s accessories that are sold in various retail stores nationwide, including partnerships with Bloomingdale’s and Neiman Marcus.
In 20 years, I will be … “The owner of a very big international clothing company that makes and sells clothes for men, women, and children.”
Best advice I’ve ever received: “The best advice came from my mentor Daymond John of Shark Tank. He told me to ‘Stay true to your brand,’ and that is important to remember because there are a lot of different opportunities that come to me, but they may not be the best for me or the mission of my company.”

6. Rachel Zietz, founder of Gladiator Lacrosse

rachelzietz Courtesy Rachel Zietz

Age: 16
The business: Gladiator Lacrosse sells lacrosse equipment, including backyard goals and rebounders. Zietz says the company is on target to exceed $2 million in revenue this year.
In 20 years, I will be … “Doing something business-related. I don’t know what the future will hold for me in 20 years, but I hope that I can look back and say that I somehow left my mark in the sport of lacrosse.”
Best advice I’ve ever received: “To always be determined to do what you want.”

7. Ben Pasternak, founder & CEO of Flogg

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Courtesy Ben Pasternak

Age: 17
The business: Flogg is a social community and virtual marketplace for teens where they can sell, buy and barter items within their network.
In 20 years, I will be … “Changing the world, building the next Apple.”
Best advice I’ve ever received:“One of my mentors Chris Smith told me to drop out of high school and move to NYC. I did and have no regrets.”

8. Shubham Banerjee, founder of Braigo Labs

shubham-banerjee-fortune-1 Courtesy Shubham Banerjee

Age: 14
The business: Braigo Labs offers low-cost Braille printers to help the visually impaired. The latest model uses Wi-Fi and Bluetooth to automatically print text from a website and translate it into Braille.
In 20 years, I will be … “In the field of a merge between technology and medicine. Surgical procedures with robotics or human health would be great for me.”
Best advice I’ve ever received: “Be humble,” and “Innovate for the right reasons — money is not one of them.”

9. Bella Tipping, founder of Kidzcationz.com

Leetina Smith-Shaw photography Photo: Leetin Smith-Shaw

Age: 13
The business: Kidzcationz is a travel review website aimed at kids, allowing them to rate hotels restaurants and attractions based on how well they support their needs.
In 20 years, I will be … “Working at [the nonprofit] Virgin Unite and fighting for social change because I want to live in a world where everyone is included.”
Best advice I’ve ever received: “I have my own motto in life: If you can think it, you can do it.”

10. Nash Grier, digital star and social media influencer

image1 Courtesy Nash Grier

Age: 18
The business: With more than 12 million followers on Vine, his wildly popular videos have landed him endorsement deals as well as book deals. He also sells merchandise on his website, including hoodies, sweatshirts and socks.
In 20 years, I will be … “A master in my craft/s—whatever I choose those to be. I just want to use my voice and my power (my knowledge) to shine light on the darkest topics, talk about what is feared, empower people, and create the best art I can—no matter the form.”
Best advice I’ve ever received: “The point of life is love.”

11. Haile Thomas, founder of Healthy Active Positive Purposeful Youth (HAPPY)

hailethomas Courtesy Haile Thomas

Age: 15
The business: HAPPY aims to improve the health and wellness of children by implementing programs that teach kids how to cook nutritious meals and promote physical activity.
In 20 years, I will have … “A televised plant-based cooking show showcasing vibrant, delicious and nutritious, plant-powered meals to the masses, to speak and share my message all around the world, and continue to motivate youth to put their passion into action.”
Best advice I’ve ever received: “Be a leader, not a follower.”

12. Cory Nieves, founder and CEO of Mr. Cory’s Cookies

corynieves4 Courtesy Cory Nieves

Age: 12
The business: Mr. Cory’s Cookies are all-natural, homemade cookies with no preservatives. They are sold through his website, and he has a number of corporate clients, including Macy’s, Aetna and Citibank.
In 20 years, I will be … “The CEO of Mr. Cory’s Cookies, and grow the business into a multi-billion-dollar brand. I also want to be an angel investor, a chef and help people all around the world.”
Best advice I’ve ever received: “Stay humble, never give up and always dream of six impossible things.”

13. Isabella Dymalovski, founder of Luv Ur Skin

Isabella Dymalovski Courtesy Isabella Dymalovski

Age: 14
The business: Luv Ur Skin is a natural skin-care line for girls developed with botanical ingredients. It includes body lotion, lip gloss, nail polish, moisturizers and more.
In 20 years, I will be … “Either running my own successful business or being in a show on Broadway!”
Best advice I’ve ever received: “Listen.”

14. Benjamin “Kickz” Kapelushnik, founder of Sneakerdon.com

benjamin-kickz Courtesy Benjamin Kapelushnik

Age: 16
The business: Sneakerdon.com is an online sneaker resale marketplace that caters to fans of high-end exclusive, rare and limited sneakers. With a roster of celebrity clients including DJ Khaled, it’s estimated Kapelushnik will bring in about $1 million in sales this year.
In 20 years, I will be … “This, but even more.”
Best advice I’ve ever received: “The best advice was from my mom: ‘Follow your dream and your passion.’”

15. Logan Guleff, food entrepreneur and winner of MasterChef Junior (season 2)

logan1 Courtesy Logan Guleff

Age: 14
The business: Guleff has a line of spice blends called “Logan’s Rub,” which has expanded to include steak and egg seasonings. He also runs an underground supper club, where he cooks for small parties.
In 20 years, I will be … “A college graduate. Then I plan to be a celebrity chef with at least one of my own television shows. I hope my books are selling well. I know my spice blends will be on every shelf. Maybe I will also be helping NASA explore the best way to colonize Mars. I really think I can help with the food for space travel!”
Best advice I’ve ever received: “First from my Mom, ‘If I can dream it, I can achieve it.’ Then from Chef [Gordon] Ramsay, ‘Find my own standard of excellence and stick to it!’”

16. Aaron Easaw, serial entrepreneur and founder of ACE Venture Capital

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Courtesy Aaron Easaw

Age: 18
The business: ACE Venture Capital is a VC firm dedicated to investing and supporting entrepreneurs under the age of 30.
In 20 years, I will be … “Doing something completely different. At that point, I’d like to focus on an industry that really interests me.”
Best advice I’ve ever received: “Don’t dwell on the past. Learn from your mistakes and move on.”

17. Benjamin Stern, founder and CEO of Nohbo

benjaminstern Courtesy Benjamin Stern

Age: 17
The business: Nohbo produces single-use, water-soluble balls containing personal care products such as shampoo, conditioner, body wash, or shaving cream. The product seeks to offer consumers an alternative wasteful plastic packaging.
In 20 years, I will be … “Doing the same thing I’m doing right now: building, growing, and investing in businesses.”
Best advice I’ve ever received: “The best business advice I’ve ever heard is the repetitive tone of my business partner and attorney, Matthew Gernstein saying, ‘You have nothing yet ’til… (always something more).’”

18. Ollie Forsyth, serial entrepreneur and founder of The Budding Entrepreneur Club

ollie-f Courtesy Ollie Forsyth

Age: 18
The business: The Budding Entrepreneur Club is an invitation-only entrepreneurs’ community for entrepreneurial individuals in the UK. Membership costs 25 euros a month. Its founder started Ollie’s Shop, an online jewelry and gift boutique.
In 20 years, I will be … “Building The Budding Entrepreneur Network up and adding umbrella companies to the portfolio.”
Best advice I’ve ever received: “If someone tells you your idea is not going to work, make it your mission to prove them wrong.”