Smart Soft Materials (SSMs) represent a pioneering field at the intersection of material science and technology, characterized by their ability to respond to various external stimuli. This chapter provides a comprehensive overview of SSMs, organized into several key areas: responsive stimuli, composition, biomimetic materials, structural classification, applications, and functional properties. The chapter begins by detailing the different responsive stimuli that drive the behavior of SSMs, including thermo-responsive, photo-responsive, pH-responsive, magneto-responsive, electro-responsive, moisture-responsive, and mechanically responsive materials. It then categorizes SSMs based on their composition into polymeric smart materials (such as conductive, electroactive, and shape-memory polymers), hybrid smart materials (composite, multifunctional, and hybrid nanomaterials), and biomimetic smart materials inspired by natural systems. Further, the chapter explores the structural classification of SSMs, highlighting hydrogels, elastomers, liquid crystal elastomers (LCEs), and composite smart materials. It examines their diverse applications in biomedical fields, soft robotics, wearable technology, adaptive optics, and smart textiles. The discussion includes specific examples of how these materials are applied in real-world scenarios, showcasing their versatility and impact. The chapter concludes with an analysis of the functional properties of SSMs, such as self-healing, shape-memory, conductive, and stimuli-responsive behavior, underscoring their potential to revolutionize various technological domains. By integrating theoretical insights with practical examples, this chapter also provides a comprehensive overview of SSMs and their transformative role in modern technology.