Four fused benzene rings. Or you may view pyrene as a -CH=CH- bridged phenanthrene. Pyrene has four different types of bond in the periphery. In the following, you will see two derivatives of pyrene that differ in the location of benzannulation: benzo[a]pyrene and benzo[e]pyrene. Both of the benzopyrenes have in common that the pyrene and the benzene share one bond.