A bio-battery is an energy storing device that is powered by organic compounds, usually being glucose, such as the glucose in human blood. When enzymes in our bodies break down glucose, several electrons and protons are released. Therefore, by using enzymes to break down glucose, bio-batteries directly receive energy from glucose. These batteries then store this energy for later use. This concept is almost identical to how both plants and many animals obtain energy. Although the batteries are still being tested before being commercially sold, several research teams and engineers are working to further advance the development of these batteries.