The Greek philosophers of Antiquity were the first to think that nature surrounding them was made of "grains of invisible matter". Among these men, Democritus went even further by giving a very pertinent definition of the atom for the time: it is the smallest indivisible part of matter (atomos means indivisible in Greek).
 

Also known as the chemist's alphabet, this table classifies every element known to man. In the rows, elements are listed according to increasing atomic mass (height of the tubes), and in the columns according to their chemical behavior.
This classification contains 91 natural elements and 25 man-made elements that you will now be able to discover. The color of the lighting depends on the physical state of the element (white for a solid, green for a gas, and blue for a liquid).