Time-lapse video microscopy was designed to follow the movement of single cells for an unlimited period of time under physiological conditions. The system is based on two inverted microscopes located in a CO(2) incubator and equipped with charge-coupled device cameras connected to the computer. Frames were recorded every minute and the subsequent video sequence was converted to database form. The system was applied to describe the movements of normal HaCaT cells and Pb-treated cells causing the so-called apoptotic dance during cell death. The apoptotic movement was also followed in high-osmolarity glycerol-type mitogen-activated protein kinase (MAPK) null mutant of Fusarium proliferatum, a filamentous fungus, during osmotic stress. The shortest (20 min) and most vigorous death movements were observed in apoptotic fungal cells subjected to salt stress. The necrotic process at higher Pb concentration (50 microM) took 2-3 h, whereas the apoptotic process at lower Pb concentrations lasted from minutes to days.