The rigidity of the substrate to which cells adhere can have a profound effect on cell morphology and gene expression. CytoSoft(R) products provide a tool to culture cells on substrates with various rigidities covering a broad physiological range. On the bottom of each well there is a thin layer of specially formulated biocompatible silicone whose elastic modulus (rigidity) is carefully measured. The surfaces of the gels in CytoSoft(R) products are functionalized to form covalent bonds with amines on proteins. This chemical functionalization is stable and the reaction does not require a catalyst facilitating the coating of the gel surfaces with matrix proteins and plating cells.The silicone substrates of CytoSoft(R) products are optically clear and have a low auto-florescence. The layer of silicone in each dish is firmly bonded to the bottom of the dish. Unlike hydrogels (such as polyacrylamide gels) silicone gels are not susceptible to hydrolysis do not dry nor swell are resilie