It is made of atoms. There are 92 naturally occuring kinds of atoms. H 2 hydrogen Atoms are small, about 10 -10 m in diameter for the smaller ones. Atoms are made of electrons moving around a nucleus.
Electrons are light particles with negative electric charge.
As far as one can determine by experiments, they have zero size. Nuclei are heavy particles with positive electric charge. Experiments show that the size of a nucleus is about 10 -15 m in diameter for the smaller ones. Nuclei are made of protons and neutrons. Positively charged particles attract negatively charged particles.