Sometimes we feel so sleep we just have to fall asleep, and that's what we want for our babies. That sensation depends on something called the Circadian Rhythm. Circadian means about a day, circa dia. And we have this hormonal tide that's in our body about every 25 hours on average. So if you were in a cave with no external cues, you would get off pace with day and night very, very quickly. But what happens is that our circadian rhythm is reset every single day to adjust to the seasons and everything go on around us to what should work out to about every 24 hours. The external cues that reset the Circadian Rhythms are called zeitgebers. And zeitgebers are a parent's best friend. Because if you know those and how to use those, you can have your child feel really, really drowsy at the right moment. Some of the strongest zeitgebers are light and temperature. Once the sun goes down, once the light goes very very dim, about 2 hours later, there's a drowsiness surge from melatonin. Turning on a light in the room for even 60 seconds destroys the melatonin surge. So a very dim house. Second thing is lower temperature, like happens naturally in the world. When the temperature lowers 7 degrees, the melatonin surge goes. So one of the best things we can do is make sure it's cooler at night for the baby rather than keeping everything at the same narrow range with our air conditioners and heaters.