This is Video S1 and it corresponds to Figure 2A. It shows that local blebbistatin micropipetting, but not DMSO, increases spine formation and extension (arrowheads). Equal volumes of blebbistatin and DMSO were used. Images were acquired every ~6 seconds using confocal microscopy. 20 frames/sec shown. A DIV 7 cortical neuron expressing DsRed2 was locally micropipetted with either DMSO or 100 mM blebbistatin at the indicated times. Note the increase in the fraction of spines that appear and extend in response to blebbistatin. Arrowheads indicate either nascent or elongating spines.