The multiplication of new organs of government, called juntas, is one of the characteristics of the second half of the 16^th century Spain. Yet, far from being a widely understood and well-known object in contemporary historiography, juntas can be considered as a secondary theme. At the crossroads of institutional studies and prosopography, this article proposes to renew the approach of these government tools from the perspective of their practices. Through the concrete example of Philip II’s personal Junta, I try to show how its rising led to enrichment under the reign of the second Habsburg of Spain. Studying the circulation of information, its treatment within the arcana of power in Madrid and the ways in which the Junta tried to influence the conciliar structure of the hispanic monarchy, this article will expose the dynamism and flexibility of a technology of power. Based on a careful study of the reports of the said Junta, our demonstration may aim to reveal the social and political stakes involved in transforming the modalities of decision and action at the turn of the sixteenth and seventeenth centuries.