<b>Appendix A.2 Single cell seeking behaviour at spheroid leading edge</b>

Time-lapse animation of bright-field images show invasion of WK1 spheroids into undiluted Matrigel™ matrix over 72 hours. Single cells at the leading edge of the invading spheroid exhibit cyclical "seeking" behaviour, detaching from collective front, then reattaching to "pull" remaining cell forward. Animated gif is 20 frames per second, time interval between frames is 20 minutes. Scale bar indicates 200µm.