Facebook CEO Mark Zuckerberg says he has built a glowing wooden box to help his wife sleep better at night, as she cares for their two children.

The invention — dubbed a “sleep box” — emits a faint light between 6 a.m. and 7 a.m., so Zuckerberg’s spouse Priscilla Chan knows the couple’s two toddler daughters are about to wake up, without having to check her phone.

“Being a mom is hard, and since we’ve had kids Priscilla has had a hard time sleeping through the night,” Zuckerberg, 34, wrote in an Instagram post. “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.”

Because the box doesn’t display the time, Chan can now fall back asleep without fear of sleeping too long. And the light is visible enough to let her know when its okay to wake up, but faint enough that it “won’t wake her up if she’s still sleeping,” Zuckerberg said.

The billionaire CEO said he shared his creation in case an entrepreneur* wants to run with the idea and build the boxes for a larger audience.

Thrive Global founder Arianna Huffington, who is an advocate for the importance of sleep, responded to Zuckerberg’s post: “It’s great that you made this device, so Priscilla could avoid looking at her phone.”(SD-Agencies)