Which branch of science studies the structure of living things?

The branch of science that focuses on the structure of living things is anatomy. Anatomy examines the organization, structure, and relationships of various parts within living organisms, which can include macroscopic structures like organs and systems as well as microscopic structures such as tissues. Understanding anatomy is crucial for various fields including medicine and biology, as it provides foundational knowledge necessary for studying how organisms function.

For instance, physiology examines how these structures work and operate, while histology deals specifically with the microscopic structure of tissues. Biology encompasses the overall study of life and living organisms but is broader than the specific study of structures. Therefore, the focus on anatomical structures clearly identifies anatomy as the right choice for this question.