The main aim of these lectures is to tri gger the interest of the restless under­ graduate student of physical, mathematical, engineering, or biological sciences in the new and exciting multidisciplinary area of the evolution of "large-scale" dynamical systems. This text grew out of a synthesis of rather heterogeneous mate­ rial that I presented on various occasions and in different contexts. For example, from lectures given since 1972 to first- and final-year undergraduate and first­ year graduate students at the School of Engineering of the University of Patras and from informal seminars offered to an international group of graduate and post­ doctoral students and faculty members at the University of Stuttgart in the aca­ demic year 1982-1983. Those who search for rigor or even formality in this book are bound to be rather disappointed. My intention is to start from "scratch" if possible, keeping the rea­ soning heuristic and tied as closely as possible to physical intuition; I assume as prerequisites just basic knowledge of (classical) physics (at the level of the Berkeley series or the Feynman lectures), calculus, and some elements of probabil­ ity theory. This does not mean that I intended to write an easy book, but rather to eliminate any difficulty for an eager reader who, in spite of incomplete for­ malistic training, would like to become acquainted with the physical ideas and con­ cepts underlying the evolution and dynamics of complex systems.