It used to amaze me that, no matter what raw materials you start with, good compost always looks the same after it is "finished".
But now I realize that basically, every bit of raw material is eaten and incorporated into some living thing (fungi, bacteria, protists, molds, grubs, nymphs, insects, worms and others). Then, OTHER living things eat the first set of living things. Rinse and repeat.
By the time it's done, it might have passed through the "gullets" of 2-5 different living things.
I respect the heck out of compost!