G'day, One possible chemical basis for the aldehyde-induced fluorescence is that the fluorophore may be the product of aldehydes reacting with the epsilon-amino groups of tissue proteins, which leads to the formationof Schiff base compounds. For further info see Hayat, M.A. 1989, Principles and techniques of electron biological applications, 3rd Ed., London, Macmillan Press. Hope this is of some assistance, Gerald Little. Dr. Gerald J. Little, The Neuroscience Group, Discipline of Anatomy, Faculty of Medicine and Health Sciences, The University of Newcastle, Callaghan, New South Wales, Australia, 2308. Ph. (61 49) 21 5618 Fax (61 49) 21 6903 Email [log in to unmask]