Basic notion and systems analysis method is briefly explained for the preparation to the understanding of the later chapters. Non-linear and linear systems equations are explained, where the standard formulation and its representation is useful for the basis of various types of modeling. Transfer function is explained for the linear system as the input-output representation. Basic graph theory is explained with its applications, where it is important to analyze large-scale metabolic reaction networks. Data analysis such as regression analysis and the principal component analysis (PCA) are also briefly explained, where it is important for analyzing the experimental data and experimental design in relation to modeling.