Mark Zuckerberg has created a "sleep box" to help his wife Priscilla Chan get more sleep because "being a mom is hard," the Facebook CEO wrote on the social media platform.

"Being a mom is hard, and since we've had kids Priscilla has had a hard time sleeping through the night," Zuckerberg, 34, wrote Saturday, alongside a photo of his invention. "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. So I worked on building her what I call the 'sleep box.' "

The wooden box lets her know whether or not she should go back to sleep or if one of them should get up and check on their daughters, Maxima, 3, and August, 1.

How does it work?

The box, which sits on Chan's nightstand, doesn't display the time. Instead, a soft light shines between 6 and 7 a.m.

"It sits on her nightstand, and between the hours of 6-7 am 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," the billionaire continued.

If the 34-year-old pediatrician wakes up in the middle of the night, she can go back to sleep without knowing the time.

"So far this has worked better than I expected and she can now sleep through the night," he wrote. "As an engineer, building a device to help my partner sleep better is one of the best ways I can think of to express my love and gratitude."

What else?

At the end of his post, Zuckerberg tossed out an offer to allow someone to take his idea and "run" with it.

"A bunch of my friends have told me they'd want something like this, so I'm putting this out there in case another entrepreneur wants to run with this and build sleep boxes for more people!" he wrote.

The post that has garnered more than 13,000 comments and nearly 10,000 shares.