The ingredients were rat heart muscle cells and a thin silicone film. ("The world needs less rats and more jellyfish, so I thought it would be cool to do a one-for-one swap," Parker joked.) Along with researchers from the California Institute of Technology, he and his team engineered the cells and silicone in a pattern that mimicked the structure of a real jellyfish. They then stuck the creature in a tank full of electrically conducting fluid and zapped it with current.
