Light micrograph of a polished surface of fusinite maceral (lithotype durain, bituminous coal) with broken cell structures, some of them are filled with clay (dark color). The coal is a sedimentary rock that occurs in stratified deposits: dead vegetation burried deep in the earth, during the Carboniferous Period, due to the high temperature and pressure, was slowly converted to coal. The solar energy stored by the plants trough the photosynthesis was located inside the coal. And it is released again during combustion. Coal is the largest source of energy in the production of electricity worldwide. Nevertheless it produces importants environmental and health effects. The clean coal technology is developed to mitigate harmful emissions to the atmosphere. Field of view size: 1.49 x 2.23 mm (0.059 x 0.088 in)