Martin Markl Mathematical Institute of the Academy, Prague Strongly homotopy bialgebras Abstract: I will explain how homotopy invariant algebraic structures (such as A_\infty algebras, L_\infty algebras, etc.) naturally arise from minimal models of corresponding operads and PROPs. I will then discuss methods to construct such minimal models and give a couple of examples of these models. The remaining part of the talk will be devoted to the theory of bialgebras (Hopf algebras without an antipode) and to the minimal model of the corresponding PROP. The study of such objects, which can be interpreted as certain kinds of graph complexes, was initiated by Maxim Kontsevich and his deformation quantization program.