British orthodontist Mike Mew and his father developed a 'mewing' technique that is designed to expand the mouth palate.
The purpose of Mewing Before and After is to have the tongue pressed evenly on the palate over its entire area. The main targeted area is the posterior third. This puts pressure on the palate that helps in structural change. The structural changes in both soft tissue and bone occur with the passage of time.
Mewing Before and After is quite popular over the internet due to its effect on facial aesthetics. The specific movement helps realign your teeth and define your jawline.
The feedback from the people who do mewing is great. They report several benefits of mewing like:
Prominent Jawline.
The second chin is gone.
Improvement in nasal breathing.
Aligned teeth (in some cases).

DOES MEWING WORK?
Mewing is a new phenomenon and area of research for many orthodontists. However, there is not a lot of research confirming or refuting the effectiveness of mewing. The feedback of people on the internet confirms the effectiveness of mewing. There are thousands of before and after photos of people doing mewing. People using this technique for a longer time claims noticeable changes in the structure of their face. The most significant part of this technique is that the people doing mewing are very satisfied with the changes.