Senator Geiss previously served two terms in the Michigan House of Representatives and then as the Democratic Caucus Chair in her first term in the Senate. Her major legislative accomplishments include improving the standards of care for pregnant and nursing prisoners at the state's only facility for female inmates, improving communication with the Federal Railroad Administration to decrease blocked crossings in her community, and developing the standards of implicit bias training for health care professionals across the state as part of a broader strategy to reduce racial disparities in health outcomes.

She earned her bachelor's degree in developmental psychology from Brandeis University and her master's degree in art and architectural history from Tufts University. She is the granddaughter of Panamanian immigrants and has spent most of her adult life in Michigan.

She and her husband, Doug, live in Taylor and have two children.