Institut Mittag-Leffler is an international centre for research and Training center in mathematical sciences for postdoctoral student.Professor Gösta Mittag-Leffler founded It in 1916 and his wife Signe, who donated their magnificent villa, with its first-class library, for the purpose of creating the Institute that bears their name. The Institute is the oldest Mathematics Research Institute in the world, operates under the auspices of the Royal Swedish Academy of Sciences but enjoys great autonomy. The area of Institute Mittag-Leffler encompasses several buildings on a park-like estate. The main building, originally the home of Gösta and Signe, is a beautifully preserved villa in the art nouveau style. In addition to the library, the building houses a lecture room and offices for staff and participants. Their mission is to support international top-level research in mathematics, with special attention to the development of mathematical research in Nordic countries. It also has a responsibility towards providing service as a contact and link between mathematicians in the Nordic countries as well as the international research community. Major activities of the Institute are research programs, conferences, workshops and summer schools. The Institute is responsible for publishing two renowned research journals, Acta Mathematica and Arkiv för Matematik. They are about to make a conferrance of Herglotz-Nevanlinna functions and their applications for the purpose of bring together mathematicians, physicists, and engineers who are interested in bounded analytic interpolation. Its focus lies on Herglotz-Nevanlinna functions in connection with passive, causal, and active systems (in particular, electromagnetic design, composite materials, and Dirichlet-to-Neumann maps) and hence the main tools are within complex analysis and functional analysis as well as convex optimization.