What did Amadeo Avogadro do?

He created 6.022X10^23 which is used to count moles.

We suppose ... that the constituent molecules of any simple gas whatever (i.e., the molecules which are at such a distance from each other that they cannot exercise their mutual action) are not...

contribution of amedeo avogadro in the field of chemistry?

Is it true that Avogadro did experiments to determine Avogadro's number?

as the amount of molecules increases so does the volume