If atoms are really tiny and are not visible to that naked eye, how did we even come to find out what atoms were?

Question: If atoms are really tiny and are not visible to that naked eye, how did we even come to find out what atoms were?
- Keywords:
- Royal Society of Chemistry: Find out more about:
  
  atom
  
  tiny
  
  visible
Asked by Lily Reigate to Alex, Anaïs, Peter, Shreesha on 19 Mar 2015.
- Peter Maskell answered on 19 Mar 2015:
  
  A short history of atoms:-
  http://www.nobeliefs.com/atom.htm
- Anaïs Pujol answered on 19 Mar 2015:
  
  By theory, The Greek Democrite was the first one to think that any matter was composed by particles invisible to eyes. It is theory comes from the fact that if you break an object you will break it until you will have the most tiny bit of matter. This theory was confirm by Dalton who reacted 1g Hydrogen and 8g oxygen to form 9g of water. For him this results explain the theory of the atoms, where matter is formed of invisible particles.

Question: If atoms are really tiny and are not visible to that naked eye, how did we even come to find out what atoms were?