Theory of structuration
Developed by Anthony Giddens, the theory of structuration notes that social life is more than random individual acts, but is not merely determined by social forces. To put it another way, it's not merely a mass of 'micro'-level activity - but on the other hand, you can't study it by only looking for 'macro'-level explanations. Instead, Giddens suggests, human agency and social structure are in a relationship with each other, and it is the repetition of the acts of individual agents which reproduces the structure. This means that there is a social structure - traditions, institutions, moral codes, and established ways of doing things; but it also means that these can be changed when people start to ignore them, replace them, or reproduce them differently.
Gauntlett, David (2002), Media, Gender and Identity: An Introduction, Routledge, London and New York. (Extracts available at www.theory.org.uk)