In this chapter, you learn how to build on your knowledge of general-purpose input/output (GPIO) and bus interfacing. In particular, you can combine hardware and software to provide the Raspberry Pi (RPi) with the ability to interact with its physical environment in the following three ways: First, by controlling actuators such as motors, the RPi can affect its environment, which is very important for applications such as robotics and home automation. Second, the RPi can gather information about its physical environment by communicating with sensors. Third, by interfacing to display modules, the RPi can present information. This chapter explains how each of these interactions can be performed. Physical interaction hardware and software provides you with the capability to build advanced projects (for example, to build a robotic platform that can sense and interact with its environment). The chapter finishes with a discussion on how you can create your own C/C++ code libraries and utilize them to build highly scalable projects.