A hydrogel can be defined as a gel in which the majority liquid component is water. More precisely, hydrogels are three-dimensional networks of hydrophilic (water loving) polymers that are crosslinked (meaning the polymer chains are connected together via physical or chemical links), enabling them to swell while maintaining their structure without dissolving.Hydrogels can be made with a wide variety of materials, making their mechanical properties tunable, and their applications versatile. This versatility is what makes hydrogels one of the more commonly used scaffolds in tissue engineering. Examples include using hydrogels as three-dimensional structures to support cells and delivery vehicles for bioactive factors.