Katetov functors; joint work with Dragan Masulovic (Novi Sad)

We shall describe a natural method for constructing Fraisse limits by iterating a special functor F such that F(X) realizes all possible ``simple" extensions of the model X in a fixed class, usually consisting of finitely generated models of a fixed first-order language.
This method had been first used by Katetov, in connection with the Urysohn universal metric space.
We shall survey some aspects of the abstract theory of Katetov functors, showing some examples, and indicating some open problems.