My main research areas are higher category theory, nonabelian cohomology, topos theory, homotopy theory and nonabelian algebraic topology.

I have a collaboration with U. Schreiber

With Z. Skoda , I coorganized a conference Categories in geometry and in mathematical physics in Split.

In my PhD thesis Bigroupoid 2-torsors I proposed a unified treatment of nonabelian cohomology theory, using the theory of 2-torsors and their simplicial interpretation as the basis for the theory of nonabelian higher torsors.
My Ph.D. advisor was Branislav Jurco Read here on Jurco's scientific interests

For an online introduction to usual category theory see Bodo Pareigis: Category theory (online notes) dvi , ps , pdf and for higher category theory see Leinster's book Higher operads, higher categories (arXiv version is here )