This book discusses recent advances in hydrogels, including their generation and applications and presents a compendium of fundamental concepts. It highlights the most important hydrogel materials, including physical hydrogels, chemical hydrogels and nanohydrogels and explores the development of hydrogel-based novel materials that respond to external stimuli, such as temperature, pressure, pH, light, biochemicals or magnetism, which represent a new class of intelligent materials. With their multiple cooperative functions, hydrogel-based materials exhibit different potential applications ranging from biomedical engineering to water purification systems. This book covers key topics including superabsorbent polymer hydrogel; intelligent hydrogels for drug delivery; hydrogels from catechol-conjugated materials; nanomaterials loaded hydrogel; electrospinning of hydrogels; biopolymers-based hydrogels; injectable hydrogels; interpenetrating-polymer-network hydrogels: radiation- and sonochemical synthesis of micro/nano/macroscopic hydrogels; DNA-based hydrogels; and multifunctional applications of hydrogels. It will prove a valuable resource for researchers working in industry and academia alike. Intro; Preface; Contents; About the Editors; 1 Intelligent Hydrogels as Drug Delivery Systems; References; 2 History, Classification, Properties and Application of Hydrogels: An Overview; Abstract; 1 Historical Background; 2 Hydrogels; 3 Classification of Hydrogels; 3.1 Classification Based on Origin; 3.1.1 Natural Hydrogels; 3.1.2 Synthetic Hydrogels; 3.1.3 Hybrid Hydrogels; 3.2 Classification Based on Composition; 3.2.1 Homopolymer Hydrogels; 3.2.2 Copolymer Hydrogels; 3.2.3 Multipolymer Hydrogels; 3.2.4 Interpenetrating Network (IPN); 3.3 Classification Based on Ionic Charge. 3.3.1 Neutral (Non-Ionic) Hydrogels3.3.2 Ionic Hydrogels; 3.3.3 Ampholytic Hydrogels; 3.4 Classification Based on Pore Size; 3.5 Classification Based on Physical Appearance; 3.6 Classification Based on Configuration; 3.6.1 Amorphous (Non-Crystalline); 3.6.2 Semi-Crystalline; 3.7 Classification Based on Cross-Linking; 4 Synthesis of Hydrogels; 4.1 Chemical Method; 5 Characteristics of Hydrogels; 5.1 Temperature-Sensitive Hydrogels; 5.2 pH-Sensitive Hydrogels; 6 Applications of Hydrogels; 6.1 Separation Technology; 6.2 Biomedical Applications; 6.3 Pharmaceutical Applications. 6.4 Agricultural and Horticultural Applications7 Biopolymers-Polysaccharides; 7.1 Sodium Alginate; 7.2 Xanthan Gum; 7.3 Gum Ghatti; 7.4 Gum Karaya; 7.5 Gum Arabic; 7.6 Carrageenans; 7.7 Chitosan; 8 Conclusions and Future Perspective; References; 3 Macroporous Hydrogels: Preparation, Properties and Applications; Abstract; 1 Introduction; 2 Classification of Macroporous Hydrogels; 3 Preparation Techniques of Macroporous Hydrogels; 3.1 Porogen Leaching; 3.2 Freeze-Drying Technique (Lyophilization); 3.3 Ice-Templating (Cryogelation); 3.4 Gas Foaming; 3.5 Electrospinning. 3.6 Other Preparation Techniques (Colloidal Crystal Templating, 3D Printing, Photolithography)4 Properties of Macroporous Hydrogels; 4.1 Swelling; 4.2 Porosity; 4.3 Mechanical Properties; 4.4 Thermal Stability; 4.5 Biodegradability and Biocompatibility; 5 Applications of Macroporous Hydrogels; 5.1 Drug Delivery; 5.2 Tissue Engineering and Regenerative Medicine; 5.3 Chromatography; 5.4 Environmental Protection; 5.4.1 Heavy Metal Ions Sorption; 5.4.2 Dyes Sorption; 6 Conclusions; Acknowledgements; References; 4 Hydrogel-Based Strategies for Stem Cell Therapy; Abstract; 1 Introduction. 2 Classifications of Hydrogels2.1 According to the Origin of Hydrogel; 2.1.1 Plant-Derived Polymer Hydrogels; 2.1.2 Animal-Derived Polymer Hydrogels; 2.1.3 Hydrogels Based on Synthetic Polymers; 2.2 Environmentally-Sensitive Polymer Hydrogels; 2.2.1 Temperature-Sensitive Hydrogels; 2.2.2 pH-Sensitive Hydrogels; 2.2.3 Electro-Sensitive Hydrogels; 3 Current Status of Stem Cell Survival After Transplantation; 3.1 Stem Cell Niches; 3.2 Hydrogel Niches and Their Application in Stem Cell Therapy; 3.2.1 Hydrogels as ECM; 3.2.2 Hydrogel with Support Cells.