This book provides an introduction to the qualitative theory and applications of partial functional differential equations from the viewpoint of dynamical systems. Many fundamental results and methods scattered throughout research journals are described, various applications to population growth in a heterogeneous environment are presented and a comprehensive bibliography from both mathematical and biological sources is provided. The main emphasis of the book is on reaction-diffusion equations with delayed nonlinear reaction terms and on the joint effect of the time delay and spatial diffusion on the spatial-temporal patterns of the considered systems. The presentation is self-contained and accessible to the nonspecialist. The book should be of value to graduate students and researchers in dynamical systems, differential equations, semigroup theory, nonlinear analysis and mathematical biology. The style of the presentation appeals especially to people trained and interested in the qualitative theory of ordinary/functional/partial differential equations.