What is the subject of Paul Cezannes work?

It is difficult to date his early paintings exactly, but the first one might be Girl with a Parrot or The Two Children, from 1859/60.
A series of wall paintings representing the four seasons were transferred to canvas and are now at the Petit Palais, Paris, France. They were painted in 1859 or 1860 and are the first (or among the first) paintings by Cézanne known today.