The Affordable Care Act was supposed to mend what President Barack Obama called a broken health care system, but its best-known programs — online insurance and expanded Medicaid for the poor — affect a relatively small portion of Americans.

A federal office you’ve probably never heard of is supposed to fix health care for everybody else.

The law created the Center for Medicare and Medicaid Innovation to launch experiments in every state, changing the way doctors and hospitals are paid, building networks between caregivers and training them to intervene before chronic illness gets worse.

The center’s ten-year, $10 billion budget is the largest ever devoted to transforming care. In several states the office is working to overhaul medicine for nearly all residents — not just those with government Medicare and Medicaid coverage.