We have developed a regulator-free device that enables long-term incubation of mammalian cells for epi-fluorescence imaging, based oil a concept that the size of sample to be gassed and heated is reduced to observation scale A poly(dimethylsiloxane) block stamped on a coverslip works as a long-lasting supplier of CO2-rich gas to adjust bicarbonate-containing medium in a tiny chamber at physiological pH, and all oil-immersion objective warms cells across the coverslip A time-lapse imaging experiment using HeLa cells stably expressing fluorescent cell-cycle indicators showed that the cells in the chamber proliferated with normal cell-cycle period over 2 days (C) 2010 Elsevier Inc All rights reserved