A controlling method, suitable for a first camera unit and a second camera unit, is disclosed herein. The controlling method include following steps. The first camera unit is triggered to generate a first media data by shooting a first image or recording a first video. In response to the first media data is generated, the second camera unit is automatically triggered to generate a second media data by shooting a second image or recording a second video. The first media data and the second media data are configured to be integrated into a third media data.