In this project we will analyze the 15M movement from a sociological point of view. More specifically, we interpret the explanatory keys of this social phenomenon, on the basis of the examination of the people’s perception of the institutional political system. For this reason a qualitative methodology has been developed through discourse observation and analysis. Assemblies have been attended in the city of Zaragoza, and materials from social networks belonging to other 15M committees have been analyzed, based on the examination of blogs, Twitter, etc. The main results show that in the genesis of this social movement there is a complex structure. On the one hand, the previous perception that people had of politics and political institutions, on understanding their ideal for their involvement in politics in an isolated and specific way. On the other hand, the consequences of the economic crisis, the rise of unemployment (especially relevant in the case of young people), and the point of view of financial institutions and markets.And lastly, the fact of the participants understanding the power of the establishing order. The ‘spontaneous’ participative processes are enriched when the citizen feels he or she is the main figure and something important for him or her is at stake.