How does fire turn into ash?

I think the fire itself, the flame, does not turn into ash. It may seem to you almost the same thing if I say that ash is left after a fire has burned. Or, we could say that fire can turn wood into ash. Actually, the ash is stuff that was there in the wood to start with, a small part of the wood that the fire could not burn.

Except for gasoline and natural gas, most of the things we burn leave some ash. Ash comes from minerals. The ash left by burning wood comes from minerals that a tree needed and took up from the soil by its roots.