Present understanding of electric transport in graphene, a crystalline layer of carbon, is reviewed. In the first part, emphasis is placed on the gap between the ideal and reality of electron transport, which is mostly caused by disorder (charged impurities) in the experimental samples. Disorder which affects the graphene transport originates mainly from charged impurities in the substrate, comtaminants on the graphene surface due to, e.g., resists and sticky tapes, and absorbed gas molecules. The amount of charged impurities and the methods to remove them are discussed. In the second part, the characteristic phenomena in multilayer graphene are explained for spins and Cooper-pair transport, which are relevant to the nonuniform distribution of the carrier density under nonzero gate voltages.
