 Hydrogels are three-dimensional networks composed of polymer chains that can absorb large amounts of water or biological fluids. They have been studied extensively due to their potential use in biosensing, drug delivery, and tissue engineering. This review discusses the advantages of hydrogels over other biomaterials, including their responsiveness to various stimuli, gelation mechanism, and mesh size calculations. Additionally, the review covers the preparation of hydrogels from natural materials like polysaccharides and polypeptides, as well as synthetic hydrogels from recently published literature. The review also focuses on biomedical applications of hydrogels, including cell culture, cell healing, and drug delivery. This article was authored by Chin Yuan Chai, Yang Jiao, and Xin Jiu and Yu.