HEPES is a zwitterionic organic chemical buffering agent; one of the twelve Good's buffers.
HEPES has been utilized extensively for research and commercial applications in the cell culture and tissue culture industries. HEPES is widely used in cell culture, largely because it is better at maintaining physiological pH despite changes in carbon dioxide concentration (produced by cellular respiration) when compared to bicarbonate buffers, which are also commonly used in cell culture. It's dissociation decreases as the temperature decreases which makes it a more effective buffering agent for maintaining enzyme structure and function at low temperatures.