Molecular biology was an area of a starship dedicated to the study of biology at a molecular level. The field overlapped with other areas of biology and chemistry, particularly genetics and biochemistry.
Lieutenant Jeffrey Fratis served in the molecular biology department aboard the USS Enterprise-D in 2369. That year Commander William T. Riker and Lieutenant Commander Deanna Troi attempted to review Fratis' crew evaluation report but kept getting distracted. (TNG: "Man Of The People")