Time-lapse imaging of Arabidopsis pollen tubes emerging from the cut portion of a pistil, fanning out, and traveling across the pollen growth medium filled in a microchannel, and then the tubes respond to ovules placed in a microchamber. The cartoon below shows the setup for this procedure. The time elapsed between two frames is 15 minutes indicated in the top left-hand corner.
Reference: Yetisen, A.K., Jiang, L., Cooper, J.R., Qin, Y., Palanivelu, R*., and Zohar, Y*. (2011). A microsystem-based assay for studying pollen tube guidance in plant reproduction. Journal of Micromechanics and Microengineering. 21 (5): 054018. Link to article or pdf file.