When combined with molecular analysis and immunocytological localization, fluorescencein situhybridization (FISH) represents one of the most direct and precise experimental tools in current biological research (1 -4 ). Direct visualization andin situdetection fill the gap between molecular analysis and cytological description and provide a new avenue for in vitro and in vivo comparison. Such a system facilitates the understanding of cellular events not only with respect to what and how, but also where and when.
