This third edition of the Maia-days addresses questions like coherence and quantum entanglement in open quantum systems (such as spin chains) embedded in a macroscopic environment. Different point of views will be exposed, namely a biological, a physical and a mathematical one, proposed by Virginia TSIOURI (University of Surrey, UK, Quantum Biophotonics group), Nicolas LAFLORENCIE (LPT, IRSAMC, UPS) and Clement PELLEGRINI (IMT, UPS). The dynamics of open quantum systems has captivated the attention of several researchers, due to essential application in quantum computing, quantum thermodynamics and quantum biology.