Set up was very easy and pT-100 Light Source was simple to operate. LEDs gave nice even illumination at 2% power. Higher powers were not necessary due to the brightness of the LED: 2% power with 5 msec or 10 msec exposure. There were no obvious signs of cell stress due to light toxicity over the duration of the 60min or 180min experiments I ran. Overall they are neat, simple to use and very efficient.