Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class nitro compounds [RmXNO2 (X=C,N,O,etc.)]
                 1 Class C-nitro compounds [R3CNO2]
                 2 Class nitramines [R2NNO2]
                 3 Class nitrates [RONO2]