This video is an introduction to Semusi's work and context aware systems. Semusi's work is at the intersection of big data, sensors and machine learning. We are building context aware mobile systems that will be aware of the context in which they operate and their behaviour will be based on the context derived from the soft and hard sensor inputs. For e.g. if we know the current context of a user is in-car we can give her location based ads that are in the radius of a mile or if we know the context is walking, we can give her location based ads that are in the range of a few hundred feet. In the smartphone era, Context is King!