It is common to assess the evolution of a country's export structure as a manifestation of the extent of progress or stagnation in its development process. Performing this exercise requires determining which features of exported products denote higher stages in that process. We argue that exports of differentiated products, especially when sold to developed countries, signal the acquisition of valuable knowledge that reflects development progress. We propose a new classification, denoted Micro-D, that works at the finest aggregation level in customs nomenclatures to provide a more precise identification of differentiated products. Specifically, the classification uses package size as a proxy for product differentiation to identify differentiated food and beverage exports. Thus, it is especially—though not exclusively—suited to capturing export upgrading in land-abundant developing countries. We apply the Micro-D classification to Argentina in 1998–2011 to deliver a new picture of the country's sources of export upgrading in this period.