In 2009, the major leaders all over the world met together for the summit on climate change in Copenhagen. A clear signal is sent to public that the traditional manner of energy consumption and economic growth needs to be changed fundamentally in the near future. In order to reach the target of reducing green house gas emission, technologies such as renewable energy sources (RES) and plug-in hybrid electric vehicles (PHEV) have to be widely adopted. For the sake of accommodating such intermittent generators and flexible loads, the transmission and distribution network of the current electric power system will be adapted toward the next generation electricity infrastructure, namely the Smart Grid, with the capability of real-time pricing, dispatching and management of demand-side response. In this paper, we first describe the Smart Grid from both the functional prospects. Moreover, the basis of the potential of the Smart Grid, a retailing spot market of electric energy is proposed. Its interoperability with other stakeholders in the electric power infrastructure, which is modeled as a cooperating multi-agent system, is elaborated.