The days of questioning whether Facebook, Snapchat, Instagram, Twitter, and other social media platforms are legitimate marketing tools are way behind us.

Those “in the know” are using social media to share their ideas, businesses, and day-to-day lives. Some of them are making millions from posting pictures online and uploading vlogs to YouTube, and others are using social media as a major strategy to scaling venture-backed startups.

The following social media influencers are all contributors to a new book called 3 Billion Under 30, brought together by 21-year-old Jared Kleinert, a TED speaker and “go to” marketing consultant for #1 NYT bestselling authors, Fortune 500 companies, and even the United Nations. Who are they, and why should you be following them? Here’s your answer.

1. Jake Paul (@jakepaul)
Jake Paul just turned 20, and yet he has over 17 million social media followers. His videos, which originally were posted on Vine and now span over Instagram, YouTube, Musically, and other platforms, have gained over 4 billion views combined, and Jake has been able to turn his social media stardom into other ventures.

He’s now the founder of TeamDom, which includes investors like Gary Vaynerchuk and Shots Studios (who’s in turn backed by Justin Bieber, Pete Cashmore, and other media titans). He’s also become a successful actor. Companies ranging from Coca Cola, Beats, Universal, and others look to Jake and his “crew” to market their products to millennials and Gen Z’ers.

2. Shonduras (@shonduras)
Shaun McBride, or “Shonduras,” may very well have been the first to partner with a corporation for a sponsored Snapchat story. Disney saw the potential for influencer marketing via Snapchat and decided to work with Shonduras to showcase their parks.

Shonduras has quickly become one of the top social media influencers on the web, most notably via Snapchat. He’s been able to leverage his following to earn revenue for his company in a variety of ways, from keynote speaking to selling merchandise, branded content, and more. Now he’s looking into different ways to push digital content creation to its limits, and have the “Best Day Ever” during all hours in his climb.

Read more: 9 Top Social Media Influencers Marketers Need to Follow