In 1955, during the summer after his fifth-grade school year, one of Miller's classmates, 14-year-old Emmett Till, was murdered by two white men while visiting his mother's relatives in Mississippi.

Miller went on to attend the United States Military Academy at West Point, New York, during a period in which very few African-Americans were admitted to the institution.

Miller went on to attend the Army's supply school, and at the conclusion of his training, Miller—then a captain—completed a 13-month tour in the Vietnam War, where he was awarded the Bronze Star for meritorious service in a combat zone.

After Vietnam, Miller returned to California, where he continued his military service as a logistics officer at the Army's Presidio base in San Francisco.

During his Senate confirmation hearing, Miller remarked that nuclear power must play a key role in the country's energy strategy.

Miller presently serves as Professor of Practice in the Department of Nuclear Engineering at Texas A&M University and is affiliated with Kairos Power.