What is a pyrimidine made of?

Pyrimidine, a ring structure composed of four carbon atoms and two nitrogen atoms, is any of a class of organic compounds of the heterocyclic series, that is also the simplest member of the family, with molecular formula C4H4N2.

The structures of several pyrimidine compounds were not recognized until 1868, although they were isolated between 1837 and 1864. Some well-known pyrimidine compounds include cytosine, thymine, and uracil, present in nucleic acids; thiamine (vitamin B1); and sulfadiazine, sulfamerazine, and sulfamethazine, drugs used in therapy of bacterial and viral diseases.