The black or color Ink Out light is flashing or on solid. If the light is flashing, the ink supply is getting low and you will need to replace the cartridge soon. If the light is on solid, the ink cartridge is completely empty and will need to be replaced in order to continue printing. Make sure you only remove the yellow tape seal from the top of any ink cartridge you install into the printer. What are the differences between Micro Piezo technology and Thermal technology? Micro Piezo technology (EPSON CARTRIDGE) differ from Thermal technologies in all areas: pressure method - electromechanical (M.P.) vs. boiling (Thermal), print head life - permanent (M.P.) vs. disposable (Thermal), ink flexibility range - wide (M.P.) vs. limited (Thermal), potential for improvement - significant (M.P.) vs. limited (Thermal). How to handle the cartridges? You should not touch the nozzles with your hands. When the cartridge sits outside the printer with unwrapped, inks will dry out, then the nozzles may get clogged. You can not get a good print output with the blocked cartridge after it is refilled.