The recent growth in graphene has witnessed the utilization of graphene as promising materials in a plethora of applications. The potential of graphene could be improved exponentially provided that the processability and band gap could be finely controlled. To this aim, chemical functionalization of graphene remains an important and fundamental approach. This tutorial review aims to provide a broad-based coverage on the recent solution-based functionalization methods of graphene in a concise and mechanistic manner. We focus on the reactions of the graphene sp(2) backbone, such as nucleophilic addition, cycloaddition, free radical additions, substitutions and rearrangements.