There is one unifying thread to all the research challenges proposed for Wimmics: the study of relations on the web. Relations between people, resources or services on the web provide a very rich source of knowledge from both the graph structure they weave and the trends of their evolutions. Relations on the web are at the heart of many powerful algorithms (e.g. PageRank), models (e.g. RDF graphs) and protocols (e.g. Open Graph Protocol). For this reason we believe that modeling, capturing and analyzing relations is a fertile research area.