This project is to design a residential duplex unit in Beijing and intents to deliver a new design concept of 2 C and 2 I. 2C is communication and coexist, 2 I is independent and interactive. Communication and coexist refer to all areas/functions in this duplex can interact together to have different possibilities. Rooms are no longer exists in an enclosed box, instead, the box can be opened to interact with each other for different flexibility. In a small duplex, all function should be clearly defined to bring out its own character, at the same time; a coherent environment should be achieved to ensure all the elements can coexist in a harmonious way. Therefore, bedroom, study room, living room, dining area is well articulated and interactive spatial arrangement among these areas is designed to encourage interactive possibilities.