 Pietilä took a diametric viewpoint to that of the rationalist school, and though the works (designed in partnership with his wife Raili Pietilä) had much of the organic idiosyncrasies of Aalto, they were far more abstract and nebulous.In arguing that nature is the apotheosis of plasticity, he demanded a morphological analysis of architectural products, considering Euclidean geometry as an inadequate instrument of analysis.His first major work, the Finnish Pavilion at the 1958 Brussels Expo did in fact take a modular approach akin to the theories of Blomstedt; however, the wooden rectangular box-like units as a whole gave a foretaste of Pietilä's later surfaces based entirely on free form; the most notable of these organic works being Kaleva Church, Tampere (1959–1966), Dipoli student assembly building, Espoo (1961–66), Metso Library, Tampere (1978–1986) and culminating in his final work, the Official Residence of the President of Finland, Mäntyniemi, Helsinki (1983–1993).