The term molecular biology was first used in 1945 by physicist William Astbury.

Molecular biology was first described as an approach focused on the underpinnings of biological phenomena-uncovering the structures of biological molecules as well as their interactions, and how these interactions explain observations of classical biology.

Molecular biology / m ə ˈ l ɛ k j ʊ l ər/ is a branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions.