The main theory behind mewing is that by changing the position of your tongue in your mouth, you may vary the form of your jawline. It is also said to assist with sleep apnea, sinusitis, and other ailments. There are many different techniques for mewing. They all involve placing your tongue against the back of your throat, just behind your nose. Mewing has become popular again because it is said to help release toxins from your body. By repeatedly mewing yourself, you open up your airways and allow more oxygen in blood cells to absorb waste products such as carbon dioxide. This can have many positive effects including reducing headaches, nausea, and fatigue. The history of mewing dates back over 1,000 years to Chinese medicine doctors. They believed that by moving your tongue back and forth across the roof of your mouth, other muscles involved in speech would be activated and your whole face would be shown movement. Today, mewing is popular among people who want to improve their appearance visually. Some find the process of mewing relaxing. It's not unusual for people to spend an hour or two at a time mewing. The frequency depends on your own personal choice, but most people start out by doing one big burst of mewing every half hour then slowing down until they get to sleep.