Matti Kortteinen is Professor of Urban Sociology at the Faculty of Social Sciences, University of Helsinki. Kortteinen’s first book was ”A High-Rise Suburb – In-Depth Study of Ways of Life in Social Change” (1982). In his later work Kortteinen has studied the national culture of work (“Fields of Honour”, 1992) and how it structures the interpretations and life of the unemployed (“Being Unemployed – A Study of Long-Term Unemployment in Finland”, 1998). Since 1998 Kortteinen has focused – together with professor Mari Vaattovaara – on the spatial differentiation of the Helsinki Region (1999–2016). Starting from ethnographic qualitative analysis Kortteinen has broadened the methological scope of his analysis to combining in depth qualitative analysis first with surveys, then to survey’s and a long-term statistical follow-ups and these, finally, to GIS-based analysis. Recent interests are focused on the social significance and results of spatial social mixing, an urban policy pursued in the City of Helsinki consistently since 1961. Kortteinen has twice been rewarded the State Prize for the Socially Most Valuable Information of the year.