The side projects of Mark Zuckerberg, from building a nightlight and a robot to his new podcast

While Synapse was just a precursor to Facebook's success, another side project called Wirehog nearly stopped Facebook before it even began TechCrunch reporter MG Siegler wrote.

TechCrunch reported that the service functioned as a "peer-to-peer file-sharing service that hooked up to Facebook," working on top of the social media platform. Early Facebook president Sean Parker stated that the service was actually illegal, and therefore a good thing the project was halted in early 2006.

"I had seen that movie before. We would have killed the baby in the cradle," he said.

Zuckerberg's side projects have focused on not just self-improvement, but also home improvement. Both Quartz and CNBC reported on Zuckerberg creating a screen-free "sleep box" for his wife Priscilla Chan.

"Being a mom is hard, and since we've had kids, Priscilla has had a hard time sleeping through the night. She'll wake up and check the time on her phone to see if the kids might wake up soon, but then knowing the time stresses her out and she can't fall back asleep," Zuckerberg said in a Facebook and Instagram post.

"It sits on her nightstand, and between the hours of 6 to 7 a.m. it emits a very faint light — visible enough that if she sees it she'll know it's an okay time for one of us to get the kids, but faint enough that the light won't wake her up if she's still sleeping," Zuckerberg continued. "And since it doesn't show the time, if she wakes up in the middle of the night, she knows to just go back to sleep without having to worry about what time it is. So far this has worked better than I expected and she can now sleep through the night."

The product ended up on Kickstarter this July, and raised over $100,000 within a month — "more than 21 times its $5,000 goal," according to CNBC.

Another — and much more extensive — project consisted of building an AI robot. According to The Observer, its functions included "recognizing his friends' faces at the door and monitoring activities in his daughter's room."

This was the same year Zuckerberg also pledged to run 365 miles, dedicating time not spent running his company to running outdoors.

Silicon Valley Business Journal reported that Zuckerberg made a goal to visit people from all 50 states. This included a variety of cities, towns, and college campuses, as well as Facebook offices across the country. By May of that year, he had already visited 20 states.

The CEO also had a similar goal in 2013 — "to meet someone new everyday outside Facebook."

Some observers questioned whether Zuckerberg's well-documented trips across the US were part of a potential future presidential bid, although Zuckerberg never addressed the rumors.

Zuckerberg's latest non-Facebook venture is a podcast called "Tech & Society." The show has four episodes thus far, and the CEO has spoken with Harvard Professors Jonathan Zittrain, Jenny Martinez, and Noah Feldman, Axel Springer's Mathias Döpfner, and historian Yuval Noah Harari.

Topics broached in the podcast have included law, journalism, privacy, democracy, and governance — critical topics in light of Facebook's clashes with Congress last year.