Staining kit for proteins and nucleic acids

A kit for use in staining proteins or nucleic acids, comprising a staining suspension consisting essentially of a sol of iron hydroxide in a medium adjusted to an appropriate concentration and an appropriate pH, and supplemented with at least one substance which promotes specific binding of the iron hydroxide to proteins and nucleic acids and, further comprising a ferrocyanide salt complex for modifying or enhancing a signal originating from the staining suspension.