**Review of Pupil** Pupil is an accessible, affordable and extensible open source platform for ubiquitous eye-tracking and gaze-based interaction. Pupil's advantages are: 1. Light-weight eye tracking headset 2. an open source software framework for mobile eye tracking 3. A graphical user interface to playback and visualize video and gaze data. 4. High-resolution scene and eye cameras for monocular and binocular gaze estimation. 5. Software and GUI are platform-independent and include state-of-the-art algorithms for real-time pupil detection and tracking, calibration, and accurate gaze estimation. After doing a performance evaluation it was shown that Pupil can provide an average gaze estimation accuracy of 0.6 degree of visual angle (0.08 degree precision) with a processing pipeline latency of only 0.045 seconds. In order to know what someone is looking at, we must to establish a mapping between pupil and gaze positions. This is what we call calibration. [[Image(p1.png,30%)]] [[Image(p2.png)]] [[Image(p3.png)]] [[Image(p4.png,30%)]] [[Image(p5.png)]] [[Image(p6.jpg)]]