The DARTER COST Action is divided into 4 Working Groups to tackle its objectives. The first 3 Working Groups deal with scientific questions (current state-of-the-art, model systems and safety and toxicology studies of delivery systems), while the last one is a capacity building Working Group (stakeholder dissemination). Another primary objective of this WG is the efficient communication of negative results: a negative results task-specific group will be set up to promote this communication by gathering data to present as posters or journal publications.