By Anupum Pant
These droplets intentionally coloured differently are different, not because of their colours, but because of different concentrations of propylene glycol and water. In this beautiful video coming from a team of researchers in Stanford demonstrates how a droplet with more propylene glycol seems to chase a droplet with more water etc. For instance, in the one where this chasing happens, which looks more like the droplets have brains of their own, the droplet with more water actually exerts a higher surface tension tug, pulling the propylene droplet along.