Researchers at Saitama University's Brain Science Institute in Japan captured the footage by utilizing zebrafish larva, which is largely transparent. The group injected a specially developed protein, which becomes visible in the presence of calcium into the fish's neuronal DNA, triggering ions to fire. This moment was captured on film. Scientist were also able to film brain cells firing in the fish's optic tectum, the portion of the brain devoted to processing eye movement, when the fish was exposed to prey fish. In other words, scientists saw the fish hunting in its brain.