Since apoptosis is a rapid process that is usually concluded within a few hours, cell culture is an adequate instrument to investigate this phenomenon as it allows us to resolve the sequence of the individual steps. Especially GFP-fusion proteins and immunofluorescence helped to reveal the dynamic processes that lead to cell death (Goldstein etai, 2000). Given the ease of studying cells in culture, even genes that have been isolated by in vivo systems, such as those of Drosophilay are subse quently analyzed in vitro (McCarthy and Dixit, 1998). This is now aided by a plethora of different readouts for apoptosis in cell culture, from the demonstration of the DNA ladder (Wyllie, 1980) or the TUNEL assay that detects the free DNA ends generated during apoptosis (Gavrieli et a l , 1992) to the exposure of surface markers in apoptotic cells (Koopman et a ly 1994). Powerful supplementary meth ods such as flow cytometry rely on cell culture and have immensely contributed to the elucidation of apoptosis (Darzynkiewicz and Traganos, 1998).