The final goal of multiscale methods based on domain decomposition, is to retain full atomistic detail only where needed (within a region of interest), while using a coarse-grained model to introduce the essential information about the surroundings dynamics. Importantly, the atomistic region becomes an open sub-system which exchanges mass, momentum and energy with the exterior. The hydrodynamics of flux exchange can be solved using an hybrid molecular-continuum description (hybrid MD) [1,2]. However, molecule exchange across the hybrid interface becomes a complicated task as one deals with more complicated molecules, essentially owing to larger steric hindrance. A way to solve this bottleneck is to combine hybrid MD with adaptive coarse-graining. The set-up is like the layers of an onion [3]: the atomistic model lies at the core, surrounded by a thermodynamically compatible coarse-grained model, which interfaces with a continuum description of the liquid (maybe also including hydrodynamic fluctuations). Finally, open boundary conditions for the continuum description [4] allow evacuation of (shear, heat or sound) waves out of the whole system, and let it behave in a grand-canonical way, in contact with the prescribed outer thermodynamic state. [1] G. De Fabritiis, R. Delgado-Buscalioni and P. Coveney, Phys. Rev. Lett.97, 134501 (2006) [2] R .Delgado-Buscalioni and G. De Fabritiis, Phys. Rev. E 76, 036709 (2007) [3] R. Delgado-Buscalioni, K. Kremer and M. Praprotnik, J. Chem. Phys. 128, 114110 (2008) [4] R. Delgado-Buscalioni, A. Dejoan, Phys. Rev. E, in press, (2008)