The structure of graphene oxide is similar to graphene containing residual oxygen, heteroatoms and structural defects. Reduced graphene oxide (rGO) can be extracted as thin film from an aqueous solution of graphite oxide (GO) slurry. Many modern procedures for the synthesis of GO are based on the Hummers method, in which graphite is oxidized by a solution of potassium permanganate in sulfuric acid. Reduction of GO using hydrazine has been reported. However, hydrazine is highly toxic and can potentially functionalize GO with nitrogen heteroatoms. Because of these issues, alternatives to hydrazine including NaBH4, ascorbic acid, and HI, among others have been used for the reduction of GO. GO can be reduced as a thin film or in an aqueous solution. Reduction methods have been recently reviewed.