In a recent posting to the confocal group, Guy Cox stated that DiI migrates along the myelin to label neurons beautifully. To clarify this, DiI migrates within the lipid bilayer but yes, it does label neurons beautifully. It has been used to stain cells in culture, and does not appear to have any toxic effects. DiI migrates along the cell membrane long before myelin appears and after myelination, the dye still migrates continually along the membrane. ANDREA ELBERGER [log in to unmask] optf