Grain legumes play a worldwide role as a source of plant proteins for feed and food. During seed mid-maturation (16-20 DAP), a semi-quantitative analysis of vicilin (globulin7S) accumulation was assessed in the model legume M.truncatula. The populations of vicilincontaining protein bodies are distinguished by their number and size which allowed proposing a model of their biogenesis. Two distributions were detected, enabling a separation of their processing at early and mid maturation stages. The largest protein bodies corresponding to mature vicilin aggregations which have probably reached their final size were shown to be formed by the fusion of the small bodies. This approach using a combined histology and statistical analysis may be useful to screen mutations of candidate genes governing storage protein content.