What types of fuel would be used in the wilderness to light a fire?

i already know that tinder must be dry, light, and fluffy. catches to a matches flame. matches must be dry, toothpick size to finger size in diameter. wood can be wet if you are adding it to a large, blazing fire. but what would be "dry, finger size to wrist size"? this is to help light a fire if you are in the wild, and you are stranded or something like that. also, this is for a science trip to estes park, colorado for science camp.What types of fuel would be used in the wilderness to light a fire?
Silver birch barch apparently makes very good kindling.

Finger size to wrist size - of thickness ranging between finger width and size of wrist.

Don't try adding large pieces of wood too early or you may risk smothering the fire.
The best thing Ive found for starting camp fires arent matches they have magnesium/flint sticks.you scrape the magnesium off into a small pile in some dry wood and strike the flint for a spark.. works like a charm EVERY time.What types of fuel would be used in the wilderness to light a fire?
what about that stuff used to light a grill?....that could work right?
First off dont use real gas fuel. Use can buy cheap compacted dry flint like material. I use that its like a big match that lights for a couple minutes. Its easy light weight and cheap. Now if you have none of that with you try to find bark and little twigs.
A very good alternative to liquid fuel is something you can make at home. Mix sawdust shavings with old candle wax. Melt the wax add sawdust. put it into an old egg carton. place under kindling and light. paper, wax, wood. Catches everytime.