Damon plays a man who is down on his luck and decides to undergo a process to shrink himself for a better life.
Payne previously directed Witherspoon to acclaim in his 1999 drama 'Election. The project is not financed at this stage. Payne, Taylor and Jim Burke are producing, said The Hollywood Reporter.
Damon reportedly plans to shoot the social satire after completing his next 'Bourne' movie.
Witherspoon had circled 'Downsizing' earlier also in 2009.