They believed that everything in the was composed of there were an of atoms differed as to their size, shape, and perhaps their weight.

The smallest basic unit of matter is said to be an atom.

Everything which is present in the universe consists of atoms and in universe infinite number of atoms are present.

Above statements are given by Democritus's. He states that the universe consists of atoms, infinite number of atoms is present in the universe and atoms can be differentiate with their shapes, size and their weight.

Thus, they believed that everything in the universe was consisting of atoms and there were an infinite number of atoms.