The talk will describe recent research on the characterization of joint extremal structures of multiple scalar functions over a common domain. Adapted from concepts introduced in the field of non-linear optimization, and motivated by applications in flow and ensemble visualization, Pareto sets over multivariate scalar fields capture jointly minimal and maximal structures. I will discuss definition, interesting properties, and algorithmic aspects of utilizing Pareto sets for visualization purposes. Finally, ongoing work will be discussed that indicates similarities to other approaches in topological analysis of multivariate scalar and vector fields, i.e. Jacobi sets and Morse critical sets.