The Concept of Time Scale -- Description of Continuous Media -- Modeling a System with a Finite Number of Variables -- General Procedure of Central Expansion for Reaction-Diffusion Equations -- Phase Space Analysis -- Models for Coupled Evolution of Temperature and Density in a Fusion Heat Pinch -- Phenomena in Resistive Magnetohydroynamics -- Coherent Nonlinear Interaction of Waves in Plasmas -- Coherent Nonlinear Coupling of Magnetohydrodynamic Resistive Modes -- Nonlinear Heat Propagation Phenomena -- Concluding Remarks.