It is a yoga breathing technique that will help you fall asleep in 60 seconds. Try to keep your tongue to the ridge of tissue just behind your upper front teeth and try to keep it the whole time.
The exercise begins by letting all the air through your mouth out. Then close your mouth breathing through your nose for 4 seconds, hold your breath for 7 seconds, and then blow air out forcibly for 8 seconds. Repeat this for four cycles.
It is a great way to fall asleep after you get up in the middle of the night for any reason. Get back in bed do the exercise, and you will fall asleep.
After 2-3 months of regular practice, there are very significant changes that happen in your physiology. It lowers heart rate, reduces blood pressure, improves digestion. Also, it is a potent anti-anxiety measure.