Structuralism
Structuralism is an early school of psychology that tried to identify the basic building blocks of conscious experience, on the idea that listing the elements of the mind could explain experience the way chemistry explains matter.
Key figure: Wilhelm Wundt. The main method was Introspection (a term coined by his student Baldwin), training observers to report on their inner experience.
Limitation
A lot of cognition happens outside conscious awareness, so introspection can only go so far.
Contrast with Functionalism, which cared less about parts and more about purpose.