or is it a myth.
We are taller in the morning than in the evening because during normal activities during the day the cartilage in our knees and other areas slowly compress, but when you go to sleep and rest the cartilage goes back to normal. On average we are about 1cm taller the morning than in the evening.
The other component to this phenomenon is that the joint capsules loose some of their synovial fluid and the connective tissues around the joints tend to become compressed throughout the day from activity and trying to counter the affects of gravity.
Also, the discs of the spine do the same thing. During the night, they resorb more fluid making them thicker and the person taller. While walking or being upright during the day, they slowly lose some of this fluid and become thinner.
Coutesy of wikiansers
Because when your sleeping the gravity stretches you.
but its only a little change in size. like.. 2mm when you lie on your back for a long enough time.. you grow its all about the gravity
it is really hard tbh to put in words how it works.
I hope I helped, :]