See, those arms serve as testers for the Labs' cancer-detecting bracelet project. For that to make sense, though, you need to understand how the system works: first you'll need to take pills packed with nanoparticles that circulate throughout the body looking for cancer cells. If they find any, they'll bind to those cells, which then literally light up. After that, the cell-particle combos make their way underneath the bracelet, since it has a magnet that attracts the nanoparticles.

Since the team wants to make sure that an illuminated clump of cancer cells is visible through human skin, they created those practice arms. They're covered in skin exhibiting different properties (thickness, etc.), as well as skin mimicking those of different ethnicities and skin tones. The bracelet probably won't be sniffing out cancer in the real world anytime soon, though, so watch the interview for now to see what it's like inside Google X Labs' Life Sciences department.