QUANTISELF is an interdisciplinary Collaborative Research Projects involving Enterprise (sociology, anthropology, information and communication science, ergonomics) that aims to analyse the role played by reflexive self-tracking technologies in order to quantify the Self or producing “Self knowledge through numbers” or Quantified Self (QS). Such devices measure, record and put together various personal data in such a way that shapes a digitized human body both through behavioral and physical activities data. It analyses the uses and design of these systems and aims to understand the actual practices and social issues in terms of appropriation and domestication of these technologies, “soft” regulation of behaviors (or “nudge”), and through the production of “computed” individuals. The QS produces a subject framed by thresholds which eventual crossing becomes a notable event, in ways shaped by viewing modes and displays. We assume that these systems produce a divided and particular way of experiencing the world in which the differences between ordinary experience (be it mobility, consumer and health) and data displayed by these devices happen not only to questioning users as well as directing them. The issues analysed by QUANTISELF therefore are as cognitive as normative In order to duly describe how such devices that put people’s bodies at the center of digital lives matter, this empirical research strives to articulate a study of the Quantified Self movement and designers of technologies with a grounded approach of users experiences and sense making process framed by individual and collective perspectives. With this aim in mind, QUANTISELF researchers articulate a large qualitative investigation about users (as many women as men) on one side and about designers and organizers of this social world on the other, with a quantitative survey dealing with both QS’ representations and practices. The investigation on uses is planned to be conducted in two waves (a year apart) and questions both the private and professional contexts of use, as well as the intertwining issues of wellness, physical and sports activities or health related at different stages of life. From the results obtained, a synthesis on “social challenges of the quantified self” will be written collaboratively by all the project partners. It will bring an original empirical and theoretical light on individual, social and organizational social issues raised by Big Data and the spread of new devices that shape the spread of personal digital devices in our society.. Following this interdisciplinary perspective, this project is articulated around three areas of research: 1) the analysis of the QS rise as a socio-political and technological original movement; 2) understand the individual experience of the people using QS tools: how does one act in a data reflexive eco-system in which technology happens to play a direct role (or not) in the reflexive making of action? And 3) a full account of the socialization forms of such experience and the place of self-quantification practices in the making and remaking of relationships and social ties. The collaborative research-Enterprise research project QUANTISELF is coordinated by the CERLIS laboratory of the University Paris Descartes and managed with Telecom ParisTech and Orange. It is expected to take place over a period of 36 months.