Book excerpt: Nonlinear semigroup theory is not only of intrinsic interest, but is also important in the study of evolution problems. In the last forty years, the generation theory of flows of holomorphic mappings has been of great interest in the theory of Markov stochastic branching processes, the theory of composition operators, control theory, and optimization. It transpires that the asymptotic behavior of solutions to evolution equations is applicable to the study of the geometry of certain domains in complex spaces. Readers are provided with a systematic overview of many results concerning both nonlinear semigroups in metric and Banach spaces and the fixed point theory of mappings, which are nonexpansive with respect to hyperbolic metrics (in particular, holomorphic self-mappings of domains in Banach spaces). The exposition is organized in a readable and intuitive manner, presenting basic functional and complex analysis as well as very recent developments. Contents: Mappings in Metric and Normed Spaces; Differentiable and Holomorphic Mappings in Banach Spaces; Hyperbolic Metrics on Domains in Complex Banach Spaces; Some Fixed Point Principles; The DenjoyOCoWolff Fixed Point Theory; Generation Theory for One-Parameter Semigroups; Flow-Invariance Conditions; Stationary Points of Continuous Semigroups; Asymptotic Behavior of Continuous Flows; Geometry of Domains in Banach Spaces."