Each year the trees later add a new layer of wood to its own structure. Certain creatures in nature change skin leaving behind the old form. In the world of trees that happens, the skin or outer timber grows old and is forming part of the deepest part of these beings.
On the outside storms and bitter cold, scorching heat and even some that another fire. All of these things in the tree produce a new cover, new cover of wood, a coat that makes the tree grow and strengthen. Fibers are necessary for the tree to take the path above excellent.
We are made a little different, but not much. We changed our skin more than we imagine, and the former is not part of our appearance. But some fire, wind, cold, heat, rain and many other unintended make our being grow.
So, every year we go up excellently.