3D cell migration of GFP-expressing cell. HT1080 cells transfected with GFP were embedded in ColI gels and migration assays were performed. Images were taken every 5 minutes for six hours. Representative movie of a GFP-positive cell is shown. The blue dot represents the current position of a tracked cell, and the blue line represents the tracked path of the migrating cell. Scale bar = 20 μm.