Seeds are at the heart of a transformation process that affects more than two billion people worldwide. This study on smallholder farmers in Tanzania examines how local seed systems are anchored in the socio-cultural structures of smallholder life worlds. Using the example of seeds, the close interweaving of agricultural and social practice is traced and it is worked out how individual processes of modernisation brought in from outside have far-reaching consequences for smallholder coexistence. The study provides a concrete, detailed and differentiated account of everyday farming life and of how smallholder households deal with seeds. A particular focus is on seed exchange relationships and how these provide both social security and social cohesion in the study region. The study is based on extensive field research and intensive interviews with farmers, who also have their own say in the work.