One day, Ms Frizzle teaches her class about the human body. After that, They go to visit a science museum to learn more about the human body. They take their school bus to go there. Everyone is excited on the yellow school bus.
On the way, they stop for lunch at a park. A student named Arnold spends too long time eating. When the other students and Ms Frizzle are all on the school bus. , Arnold is sill eating class except Ms. Frizzle pushes a strange little button（按钮）on the bus. Suddenly, the bus and Arnold because very small. They fall into a piece of cheese（奶酪）! And Arnold eats the cheese!
At first, the students are very afraid. Some girls even cry, But Ms. Frizzle tells the students just to see the body as a museum. They then touch the stomach（胃）, swim in the blood（血液）and rush to the brain（头脑）. There the class get off the bus and climb down the bones. Later, they get on the bus again and come to nasal cavity（鼻腔）.
At the same time, Arnold has to walk back to school by himself. With a sneeze（喷嚏）, Arnold sends the bus out of his body, and the class go out through his nose! They met Arnold later. The class can now draw a map of the human body.
