Trajectory of a fly in 3D space. A young (one day old) 3xP3-GFP fly was tracked for 30 seconds using visible (blue) light and GFP fluorescence, including a 10 second interval where the GFP fluorescence data was not utilized (indicated in dark green). Circles indicate the location of the fly at each 1/4 second (250 ms). (A) Trajectory plotted in three dimensions. (B) Trajectory plotted in two dimensions, top-down view. The location of the wall of the vial is indicated with red dashes. Arrows and labels indicate regions of the trajectory that represent flight and hovering, as well as regions that most likely represent walking.