Hydrogels are swollen, crosslinked networks that have great potential for use in biomedicine. Their softness, biocompatibility and ability for rapid diffusion of molecules make them useful for drug delivery, cell culture, wound healing and sensing applications. The chemical functionality of the gels can be easily modified to provide signalling and growth factors for cell proliferation. To allow the ingress of large cells, either porosity of the substrate can be controlled, or the gel can be made biodegradable. One ultimate goal is the growth of entire organs in the laboratory for eventual transplantation. Gels can be used as drug-delivery vehicles, either as implantable depots, or as microgels in blood-based delivery systems. One expanding area is the use of gels as surgical aides to prevent bleeding, infection and post-operative complications.