Hydrogels are a type of soft material that consist of an entangled 3D network with a substantial amount of water trapped within. Both small molecules (peptides, nucleosides, oligosaccharides etc.) and macromolecules (alginate, PEG, DNA, polyacrylamide etc.) are found to form hydrogels, many of which are highly biocompatible and biodegradable. Due to their broad applications in medical fields, there has been great interest in utilizing hydrogels for tissue regeneration, bioimaging, 3D-printing, drug delivery, medical adhesives, etc.. Research in hydrogels is highly interdisciplinary, which integrates expertise from chemistry, material science and engineering, biology, medical science, and physics. This collection aims to highlight common techniques in the biomedical research of hydrogels. The content can range from hydrogel synthesis and characterization to utilizing the material for particular biomedical applications. Better understanding and visualization of these techniques can efficiently guide and standardize similar research in the future.