The theory of complex systems, such as neural assemblies or lattices o
f chaotic oscillators has generated many new problems including the sy
nchronization or regularization of the cooperative behavior of systems
consisting of chaotic elements, regular spatial patterns in ''chaotic
'' lattices; and so on. A number of these problems were discussed at t
he International School in Nonlinear Science-95 (Nizhniy Novgorod, Rus
sia). In this overview we try to formulate some of the most interestin
g problems that were discussed at that meeting. (C) 1996 American Inst
itute of Physics.