The chapter discusses the concept of self-organization in biological systems, emphasizing the spontaneous emergence of spatio-temporal order and the formation of various patterns. It highlights that biological systems, including cells, exhibit coordinated behavior and generate ordered morphological patterns, which are essential for biological morphogenesis. The text reviews the theoretical and experimental evidence for self-organization in both living and nonliving systems, such as the Belousov-Zhabotinskii reaction and dissipative structures in open nonequilibrium systems. It also explores the role of complex network systems with nonlinear dynamics in self-organization, particularly in gene regulatory networks and morphogenetic interactions during development. The chapter further discusses the principles of biological self-organization, including the chaotic dynamics and attractors in nonlinear systems, and the hierarchical and modular nature of biological processes. It examines the self-organization of excitable media and associations of organisms, such as bacterial colonies, eukaryotic unicellular organisms, and animal populations, highlighting the formation of complex spatial patterns through chaotic dynamics and collective behavior.The chapter discusses the concept of self-organization in biological systems, emphasizing the spontaneous emergence of spatio-temporal order and the formation of various patterns. It highlights that biological systems, including cells, exhibit coordinated behavior and generate ordered morphological patterns, which are essential for biological morphogenesis. The text reviews the theoretical and experimental evidence for self-organization in both living and nonliving systems, such as the Belousov-Zhabotinskii reaction and dissipative structures in open nonequilibrium systems. It also explores the role of complex network systems with nonlinear dynamics in self-organization, particularly in gene regulatory networks and morphogenetic interactions during development. The chapter further discusses the principles of biological self-organization, including the chaotic dynamics and attractors in nonlinear systems, and the hierarchical and modular nature of biological processes. It examines the self-organization of excitable media and associations of organisms, such as bacterial colonies, eukaryotic unicellular organisms, and animal populations, highlighting the formation of complex spatial patterns through chaotic dynamics and collective behavior.