In this chapter, we discuss interactive visualization of big data. We will talk about why this has recently become an active area of research and present some of the most promising recent work. We will discuss a broad range of ideas but will make no attempt at comprehensiveness; for that, we point readers to Wu et al.’s vision paper [25] and Godfrey et al.’s survey [9]. But before we get there, let us start with the basics: why should we care about visualization, and why should it be interactive?