Ding-ding-ding! [Win waves a finger in the air, mimicking the sound of a ringing bell.] You got it!

When the solution evaporates, it forces the salt that was in it to crystalize outwards, because it has nowhere else to go.

[Rin points to one of the trees that's in the middle stage of growth, small clusters spiking out from the branches.]

The blue material you mixed in is a colloid. It looks like a liquid, but it actually has tiny particles in it, and these particles make the salt crystals grow faster.