In the last nine years, I’ve reviewed nearly 1,000 products for The New York Times. Can you guess what every single one of them has had in common?

All of them were intended for use while you’re awake.

Today, the exception.

Studies show that about half of all Americans don’t get the recommended amount of sleep. ( For adults it’s seven to nine hours.) And as we stumble our way through each day, groggy and cranky, we pay a terrible price in our relationships, productivity and health.

Science has learned all kinds of things about sleep. We now know, for example, that during the night, we experience several cycles of different kinds of sleep. There’s REM (rapid eye-movement) sleep, which restores and refreshes our brains. There’s deep sleep, which restores and refreshes our muscles. There’s light sleep, which is better than nothing. And there are all those times we wake up but don’t even remember we slept.

Now, to find out why you feel so wretched in the morning, you could go to a sleep lab, pay thousands of dollars, and spend the night hooked up to wires and sensors. Or you could pay $400 and get yourself a Zeo alarm clock.