Our temperature stage consists of a water-circulating heat sink and peltier thermoelectric device (Custom Thermoelectric, Bishopville, MD) and a PID-type controller unit (Oven Industries, Mechanicsburg, PA). Water is circulated through the heat sink using a garden fountain pump (available at hardware stores) submerged in a bucket. Temperature is measured with a thermistor probe calibrated to work with the controller mounted on the copper plate close to the sample. The sample, placed between two coverslips, is adhered to the copper plate near the thermistor and the assembly is placed, sample down, on a standard Olympus inverted microscope stage and is fastened with clips to prevent drift. We have also constructed stages where the plexiglass thermal insulator was replaced by rubber or cork simply adhered to a metal plate.