Sebastian volunteers to be the test subject for their experiment in human invisibility and injects himself with an invisibilitiy serum. The layers of his body disappear one-by-one, revealing the inner workings of the human body.
Teacher Suzy sings about muscles. The song mentions that muscles are everywhere throughout our body, and each muscle serves a purpose. The video provides an illustration of the muscular system and explains some common actions that muscles help us perform, such as smiling.