In this timelapse, we see hydrogel beads expanding as they absorb water. There are some interesting subtleties to the physics here. Notice how, in the Petri dish segments, the beads shift from a single crystalline structure to several smaller structures. I suspect those shifts are driven by the dropping water level, which changes how surface tension interacts with the beads’ shape to create attractive forces between beads.
Another interesting point comes as the beads expand through and out of the glass of water. Initially, the water level doesn’t change in the glass. This is because the water beads are taking up the same volume as the water that they’ve absorbed. But once the beads emerge past the water’s initial height, the water level drops dramatically. That’s because the beads are still absorbing what little water is left and continuing to expand in volume. (Image and video credit: Temponaut)