the squid in question — a Longfin Inshore — has three varieties of chromatophore colors: red, brown and yellow. Each cell is surrounded by several muscles that, when stimulated, contract to reveal the pigment within the cell. The scientists used an iPod nano as the stimulator, connecting the headphones — minus the ear buds — to the squid’s nerve through a suction electrode. Next, they scrolled to Cypress Hill’s 1993 hit “Insane in the Brain,” turned up the volume, and hit play.