He completed his PhD in 1938, and his thesis was titled "The Far Infrared Absorption Spectrum and the Rotational Structure of the Heavy Water Vapor Molecule."

From there, in 1943 he joined the American Friends Service Committee in Philadelphia, living at the Pendle Hill Quaker Center for Study and Contemplation, and training a new China humanitarian unit.

[2] However, with the adoption of the Starnes Rider, Congress denied conscientious objectors the opportunity to serve abroad, and the China unit project was cancelled.

During his career, he served as chairman of the Physics Department and Director of the Infrared Spectroscopy Research Laboratory, and directed the university's summer institutes for more than 28 years.

[1] Nelson and Marian Fuson remained dedicated to various social and political causes during their lives, particularly related to the Civil Rights Movement and the sit-ins and other protests centered in Nashville, Tennessee.

Nelson Fuson also served as chairman of Nashville's branch of the Fellowship of Reconciliation, and facilitated donations and other involvement from outside groups looking to support the cause.

Along with Fisk faculty including the historian August Meier, the Fusons were on the membership committee for the National Association for the Advancement of Colored People.

[2] The Fusons also pledged support for fellow Fisk University faculty member Lee Lorch, a mathematics professor who had refused to appear before the House Un-American Activities Committee after he and his wife had attempted to enroll their daughter in an all-Black school in Nashville.

[9] Fisk graduate students in the infrared laboratory led by Fuson and James R. Lawson also were a major part of the integration of the Southeastern Section of the American Physical Society.

The couple met while Fuson was stationed at the Pendle Hill Quaker Center for Study and Contemplation, in Wallingford, Pennsylvania, with the Civilian Public Service.