The operation of internet presupposes a material infrastructure which consumes natural resources and harms the environment. Online activity contributes to the increase of CO 2 emissions, despite the ecological awareness users may promote through social media platforms. eCO 2 system is a data- driven installation that reflects on internet materiality and the physical impact of our digital activity. It consists of an aquarium containing a micro-scale ecosystem of fish. Parameters of the ecosystem change dynamically according to real-time data retrieved from Twitter. Tweets that promote climate change awareness deteriorate the conditions of the ecosystem, thus rendering visible the impact of internet materiality. eCO 2 system is the 3 rd installation of the Social Things series, which consists of data-driven objects that dynamically change their appearance or functionality and reflect critically on the impact of technological mediation of online communication. During the online edition of the 16 th Athens Digital Arts Festival a graphical interactive simulation of the installation will be presented.Peqpez.net (caterina antonopoulou) is a media artist, engineer & researcher. Her artistic work consists of an open, dynamic process that explores everyday practices & social interactions through the creative-critical-ludic-ironic appropriation of technology. Her work includes processes of post- production of everyday objects and reappropriation of narrative fragments (from archives, memories, internet sources). Her artworks are hybrid (phygital) and draw inspiration from subjects such as everyday life, political actuality, technological mediation of social interactions & personal/collective (hi)stories. Peqpez applies and supports DIY/DIWO practices & opensource tools. She is currently an adjunct lecturer of digital art at the Department of Digital Arts & Cinema, University of Athens. She holds a master's in digital arts (UPF, Barcelona 2009) & a diploma in computer engineering (NTUA, Athens 2006). Her artistic practice feeds her PhD research on the field of media art.