Sociology is the scientific study of society, including patterns of social relationships, social interaction, and culture. It is a social science that uses various methods of empirical investigation and critical analysis to develop a body of knowledge about social order, acceptance, and change or social evolution. Many sociologists aim to conduct research that may be applied directly to social policy and welfare, while others focus primarily on refining the theoretical understanding of social processes. Subject matter ranges from the micro-sociology level of individual agency and interaction to the macro level of systems and the social structure. The traditional focuses of sociology include social stratification, social class, social mobility, religion, secularization, law, sexuality, gender, and deviance. As all spheres of human activity are affected by the interplay between social structure and individual agency, sociology has gradually expanded its focus to other subjects, such as health, medical, economy, military and penal institutions, the Internet, education, social capital, and the role of social activity in the development of scientific knowledge.