porphyrin (thing)

           
          H           H           H
           \          |          /
            C -- C == C -- C -- C
          //     |         ||    \\
      H - C      |         ||     C - H
           \     |         ||     /
            C -- NH         N -- C
           //                    \\
      H - C                       C - H
           \                     /
            C == N        HN -- C
           /     |         |     \\
      H - C      |         |      C - H
           \\    |         |     /
            C -- C == C -- C == C
           /          |          \
          H           H           H       
                      

                  Porphyrin

               
             CH2
           //
          C           H           CH3
           \          |          /
       H    C -- C == C -- C -- C     H    H
       |  //     |         ||    \\   |    | 
   H - C- C      |         ||     C - C == C - H
       |   \     |         ||     /
       H    C -- N-        N -- C
           //                    \\
      H - C           Fe2+        C - H
           \                     /
      H     C == N        -N -- C
      |    /     |         |     \\
  H - C - C      |         |      C - CH3
      |    \\    |         |     /
      H     C -- C == C -- C == C
           /          |          \
          C           H           C       
           \                     /
            C                   C
           /                     \
          C=0                  O=C
          |                      |
          OH                     OH

                  Haem