In a near-future society, scientists have developed a revolutionary technology to combat overpopulation and the environmental crisis: downsizing. This irreversible process shrinks people to a height of five inches, allowing them to live in miniature communities that greatly reduce their impact on the planet's resources. Some people opt for downsizing out of ecological concern, while others are enticed by the notion that in a smaller world, their modest savings will exponentially increase in value, granting them a life of luxury.

An occupational therapist named Paul Safranek decides to undergo the procedure along with his wife, Audrey, after financial struggles and the allure of a better life captivate their imaginations. However, things take an unexpected turn when Paul emerges downsized and discovers that Audrey has backed out at the last minute, leaving him to navigate this tiny new world alone. In his palm-sized existence, he must come to terms with his new reality and identity, befriending his hedonistic neighbor Dusan and his housecleaner Ngoc Lan, a Vietnamese political activist who was downsized against her will. These encounters lead Paul to an awakening about the true meaning of fulfillment and the complexities of the world, regardless of its scale.