Hydrogel system, as one of the most important biomaterials, is widely studied because of its tremendous potential
in regenerative medicine conferred by its wide range of malleable biochemical and physical characteristics, which include
its biocompatibility with the elemental biomolecules in vital tissues, its high water retention capability and adjustable
soft-tissue-like physicochemical properties. These properties are modifiable to facilitate the targeted tissue protected
from external damaging disturbance and having the encapsulated cells’ physiology-functional phenotypes induced or
maintained in situ. Recently, hydrogels are increasingly used in the R&D of regenerative medicine to build complex tissue.
Most of the insightful work focuses on how to select and fabricate the hydrogel models with desired physicochemical
properties, flexibility of auto response to various bio-stimuli, and capability of efficiently forming the complex tissuemimicking
construct at different scales. The present review introduced the major types of hydrogeis, the desirable physicochemical
properties, the current fabrication methodologies and special organ-based cases of applications of hydrogels,
which are used in complex tissue engineering. In addition, this review also discussed the major hurdles faced by the R&D
of hydrogel systems for complex tissue medicine.