The aim of this article is to put Torsten Hagerstrand's contribution to the development of the activity approach in transport geography into the context of his development of time-geography as an integrative ecological world view. This is discussed from a biographical perspective where experiences in his everyday life and scientific investigations are linked into a theoretical whole. The theoretical approach of Hagerstrand can be traced to experiences several years before he presented his time-geographic approach. He studied conditions for individuals' existence in different geographic, social, and ecological contexts by engaging new methods and cross-fertilizing research fields; he developed precise concepts and a notation system general enough to describe any kind of individual and applicable at different levels of aggregation. He combined theoretical and methodological developments in science with active involvement in the Swedish planning model in various sectors, not least urban and transport planning - at the same time as he criticized the fragmentation of society into separate sectors for policy and planning purposes. The article shows that Hagerstrand's early sources of inspiration were in his struggle to develop both a precise and general time-geographic approach. The activity approach in transport research is ingrained in time-geography since the extension of and distance between locations of resources make transport inevitable. Hence, the human needs of transport are generated from activities in people's everyday lives. Hagerstrand's activity approach was developed in an era when transport prognoses based on the development of demand for transportation as such prevailed. Today, the activity approach is a dominant strand in transportation research.