Medicaid and CHIP provide health coverage to nearly 60 million Americans, including children, pregnant women, parents, seniors and individuals with disabilities. In order to participate in Medicaid, federal law requires states to cover certain population groups (mandatory eligibility groups) and gives them the flexibility to cover other population groups (optional eligibility groups). States set individual eligibility criteria within federal minimum standards. States can apply to CMS for a waiver of federal law to expand health coverage beyond these groups.