The title of the book: "Hydrogel Synthesis and Applications" is composed of a few words summarize the contents of this simple book. Hydrogels have received considerable attention in the past 30 years, due to their exceptional promise in many applications. Hydrogel is a water-swollen, cross-linked hydrophilic polymeric network produced by a simple reaction of one or more monomer or by hydrogen bonds and strong Van Der Waals interactions between polymers chains. Hydrogel has a great importance for its enormous applications in the different fields. For example it may be used in agriculture, medical and biomedical application, waste water treatment.