# What principle underlies stoichiometry?

$\text{Conservation of mass....}$
...or $\text{garbage in equals garbage out}$, or $\text{TANSTAAFL}$, $\text{there ain't no such thing as a free lunch....}$
This idea of $\text{stoichiometry}$ is developed here, and also here. All chemical reactions, and representations thereof, conserve (i) mass, and (ii) charge.