The　arising　technology　eye　tracking　has　been　blooming　not　only　in　the　medical　field　but　also　in　the　field　of　computer　science.　There　are　various　usages　of　eye　tracking　that　range　from　human　study,　over　usability　of　design,　up　to　controller　input　of　computer　interfaces　to　information　security.　In　this　paper,　the　application　of　the　real-time　gaze-base　technique　eye　tracking　is　introduced　with　the　presented　usages.　A　comprehensive　summary　shows　the　progress　of　this　innovative　technology.　Finally,　the　challenges　and　potential　directions　of　this　uprising　tool　are　being　discussed.