You’ve probably never seen a sea urchin like this. This cross-section of a juvenile purple sea urchin may resemble a drone’s-eye view of a Blade Runner cityscape, but it’s actually a microscopic image created through a method called immunofluorescence. This technique allows researchers to stain molecules with fluorescent dyes, illuminating and differentiating the various networks within an animal. (Here, for example, muscle fibers appear in cyan, or bright blue, while the nerves are yellow.) And then they’re able to follow that entire yellow nerve network throughout the animal’s body (as…
