Who was Avogadro?

 Amadeo Avogadro was an Italian scientist who suggested in 1811  
 

• that equal volumes of gases contain the same number of particles
  
• that molecules could be comprised of simpler units known as atoms.

This work was ignored until after his death, when Stanislao Cannizarro recognized the significance of Avogadro's ideas.  Avogadro himself knew nothing about moles, but the constant that gives the number of entities per mole was named after him in honor of his contributions to chemistry.