Neuron Under Glass Necklace. Neurons are the ultimate transmitting cell structures in our brains. They allow us to think, move, and interpret the world around us. While we have approximately 80 billion neurons in our brains, this archival-quality print of a pyramidal neuron is placed under a a 1 inch glass dome, giving the image a 3-D quality. The metal in the pendant is a lead-free, nickel-free alloy, and it comes with an 18 inch steel snake chain. A great gift for any medical or neuroscience fan.