Fibroblasts on spider silk. Coloured scanning electron micrograph (SEM) of fibroblasts growing on a layer of spider silk, produced by genetically modified bacteria. Fibroblasts are cells that produce connective tissue such as collagen, the main structural protein in the body. This silk has excellent cell adhesion properties and therefore has many applications including in wound dressing, implant coatings and drug delivery systems. Magnification: x670 when printed 10 centimetres wide.