During the anaerobic fermentation process, micro-organisms break down (macerate) organic matter (biomass) in an oxygen-free, carbon dioxide-rich environment. Nearly all coffee undergoes some fermentation of its fruit. Coffee cherries enter fermentation in the "honey-processed" stage. Producers attempt to control and modulate the fermentation process with various passive open-air containment methods or on drying beds. The difference with anaerobic fermentation is that the coffee is contained within vessels that remove all oxygen at the beginning of the process and release CO2 that builds up throughout the fermentation process. This process creates a different flavor profile than traditionally fermented coffee.