Methane is the second most important greenhouse gas after CO2 and it accumulates in the atmosphere at an alarming rate. Half of the methane produced per year is generated by microorganisms called methanogens. Methanogens generate energy by converting CO2 to methane and to do so, they use a complicated machinery of different enzymes. The last reaction performed by this machinery liberates methane and is performed by the enzyme methyl-coenzyme M reductase (MCR), which is common to all methanogens on Earth. Chemically, this is an extremely challenging reaction and is the bottleneck in methane formation by methanogens.