Despite the importance of new concept development (NCD) literature, the variety and evolution of concepts generated in the fuzzy front end and that lead to the concepts that will be design briefs for new product, technology and radical innovation projects is still misunderstood. In this paper, we propose to address this issue of multiplicity and coherence of emerging concept descriptions in the fuzzy front end at three levels of analysis — cognitive, managerial and strategic — in order to describe the dynamics of conceptual works. We rely on a longitudinal study (8 years) of the innovation capability management in a large established firm, SNCF, the French railroad company. Our main results are i) to give a typology of emerging concept formulations; ii) to elicit a structured process of building a “desirable unknown” for both the firm and involved individuals, that gather three dimensions: cognitive generative power, collaborative attractiveness for new organizations experimentation, and strategic positioning renewal of the firm in quickly evolving environments; and iii) to explicit specific patterns of emerging concept that can improve the performance of design briefs. We thereby contribute to guide practitioners involved in NCD work to reach their innovation goals.