This book is the result of an International conference gathering the most recents results in this field. The studies on Biohydrogels have had a rapid, exponential evolution in the last decades. Starting from one of the first applications of hydrogels in surgery, polyvinylalcohol crosslinked with formaldehyde under the trade name of Ivalon, we passed through PolyHema hydrogels as contact lens materials, hydrophilic polyurethanes (HPU), biodegradable hydrogels for both reconstructive surgery and pharmaceutical delivery systems, and finally more recently, one decade old, the thermoreversible and transient network hydrogels. Of course all these classes of hydrogels have been always and continuously studied, improving their performance and field of applications. Recently, most of them have been used as scaffolds for cells, even stem ones, for regenerative applications (tissue engineering). Nevertheless hydrogels are odd materials and many studies still have to be carried out to fully understand their behaviour from mechanical, physicochemical and biological point of view.