A hydrosoluble mold-release agent for use in the flat embedding of micro-organisms, and as a replacement for the coating of glass slides to produce a smoother, even surface. The reference below describes the selection and precisely oriented sectioning of single cells by light microscopy, prior to examination by EM. Reymond, O.L. & Picket-Heaps, J.D., (1983) J. Microscopy, 130, 179.