What is eminent domain and what does the Fifth Amendment require before the government takes private property?

The Fifth Amendment's Takings Clause states that private property shall not be taken for public use without just compensation. Courts have interpreted 'just compensation' to mean fair market value at the time of the taking, which is what a willing buyer would pay a willing seller in an arm's-length transaction. The Supreme Court's controversial Kelo v. City of New London (2005) decision broadened the definition of 'public use' to include economic development projects benefiting private parties, sparking significant public backlash and prompting over 40 states to pass laws restricting the use of eminent domain for private economic development.