Final answer:
The term describing the study of complex systems by analyzing constituent parts and their functions differs depending on the context; broadly it's called reductionism,
Step-by-step explanation:
The term that describes a study which breaks down a complicated thing into its constituent parts, identifying each part's function, could be referred to as reductionism in a general scientific context. However, specific fields of science have their own terms.
In biology, a process akin to this description would be a histological study when referring to tissues, or more broadly, structural biology when referring to the molecular structure and function within an organism. For example, the initial physical breakdown of an apple in the body is part of the digestive process, specifically mechanical digestion involving physical fragmentation.
Yet, to understand the comprehensive structure of an organism, one would study it from the smallest parts, such as atoms and molecules, up through cells, tissues, organs, and organ systems, following the methodology of biology's fundamental levels of organization which progressively increase in complexity.
while histology is used for tissues studies in biology, and structural biology for examining molecular structures and functions within living organisms.