The single-photon avalanche diode (SPAD) is an emerging image sensing technology with unique capabilities relevant to computer vision applications. Originally designed for imaging in low-light conditions, the ultra-high time resolution of SPADs also helps to achieve extremely high dynamic range, motion blur-free images and even seeing around corners. The use of SPADs in recent iPhone models has spurred increased interest in the use of SPADs in commercial products. In this talk, we introduce SPAD-based imagers, explain how they work, present their fundamental capabilities, and identify their key strengths and weaknesses relative to conventional image sensors. We also show how they can be used in a variety of applications.