Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class nucleic acids [[─P(=O)(OH)OCH2CH(O~)CH(O─)CH(Y)CH(base)~]n (Y=H or OH)]
                 Class ribonucleic acids [[─P(=O)(OH)OCH2CH(O~)CH(O─)CH(OH)CH(base)~]n]