"De natura rerum" is an encyclopedic work – thus belonging to the encyclopedic genre, largely widespread on the Latin Late Middle Ages – that wants to represent a complete and exhaustive compendium of the previous scientific history, specifically for clergy.A first 'stable' redaction of the work is dated between 1237 and 1240 (as to say, in the period when Thomas is located at the Dominica "studium" in Paris) and it's structured into nineteen books.