In this thesis, I view the global Fashion System in terms of hybridity, with the intention of developing a theoretical understanding of a sustainable fashion system. I explore a perpetuated micro-scale activity – getting dressed each day – as a driver of the fashion system. Thereby aiming to help in redefining and clarifying the dynamics of fashion as a complex social-ecological system, to inform of risks and opportunities towards sustainable fashion. This project has two strands; Firstly, a theoretical understanding of fashion as a social-ecological system emphasizing social and abstract representations. Secondly, an action-oriented research approach for understanding how the frameworks applied in a science-business collaborative project relate to sustainable fashion and how that affects their work. For this, I draw on Critical Realism as meta-theory, where the real world consists of both material and non-material stratified layers.  Dividing the fashion system in four stratified layers; physical, material interaction, socio-economic and culture, allows the bridging of theory and practice. I argue that three concepts hybridity, modernity and fashion are essential for visioning a future sustainable fashion system and that key social-ecological resilience theories are limited for weaving them together. I found that transformations towards sustainable fashion cannot be reduced to merely socio-technical solutions, as individual’s everyday perpetuated activity of getting dressed is linked to global negative environmental impacts. In the science-business collaborative project, key challenges were identified: inadequate amount of time, and absence of knowledge regarding the fashion industry and fashion theory as well as absence of critical reflections. Finally, I found that the concepts of affordances provide a useful link between human, ‘things’ and the abstract entities created through the value chains of the fashion system. Thus, I propose that affordances could be developed as a tool linking sustainability science, design studies and economic business models, enhancing knowledge in science-business collaborations.