Rings

When he was stoned, Matt believed if he cut off the tip of his finger it wouldn't bleed. He would be able to cut through it with a butter knife and it would be like slicing a piece of cheese, and on the inside of the digit there wouldn't be muscles and nerves and veins, but instead it would be smooth and covered in concentric rings, like a tree. One for each year of life.

He could look at the rings and see that he was fat when he was 8, but impossibly skinny when he was 18, because one would be bigger than the other. The year he dropped out of high school would be slightly darker than the rest, and the 13th ring would have the faintest shade of green because that's when he started smoking pot. 

Matt wanted to know what his friend's rings would look like, how the events of their life left marks that could only be seen by them. He could never ask them though. They wouldn't take it seriously. They wouldn't care like he did.