Similar cups available here- some change with hot water, some with cold:
From Amazon: BUY NOW: Cherry Blossom Color Change Cup
Check out these other thermochomic physics toys
Cherry Blossom Sake Cups: ice cold liquid produces blue blossoms on the initially bare branch, but pour in a hot beverage and the branch fills with pink flowers! The designs at the bottom of these ceramic color-changing cups employ leuco dyes, thermochromic chemicals that have reversible forms, one colorless.
Get a PhoTOP here (comes with laser pointer!):
From Vat19: BUY NOW: PhoTOP
Another amazing spinning device by Prof. Ken Brecher! Get his other spinning tops here:
From Etsy: BUY NOW: PhiTOP, PiTOP, eTOP, iTOP, DeltaCELT
The PhoTOP: phosphorescent glow illuminates the intricate path of a 405nm laser pointer beam on a balanced spinning disk. Let the disk set alone for a few minutes to allow the traces to fade- and repeat again and again to experiment making new patterns.
Get this inexpensive version that makes big sparks!
from Engine DIY: BUY NOW: Wimshurst Electrostatic Generator
Wimshurst Electrostatic Generator: this device uses two counter rotating disks of metal pads to separate charge via induction. The repulsion felt by electrons as the triangle plates pass by each other pushes charge to flow across two conducting rods, one on each side, which allows the charge to stack up. This excess charge is then stored in old fashioned cylindrical capacitors (Leyden Jars) until the resulting 30,000+ Volts is achieved to jump the air gap. This device goes back to 1883- invented by James Wimshurst