Note that the latest version of AdResS, which we will refer to here as TR-AdResS, differs in two respects from the above description (see e.g. Fig. in Ref. 78): (i) the CG molecules are replaced by so-called tracer (TR) particles that are exempt of non-bonded interactions and only subject to an effective pre-calibrated one-particle force that maintains a correct homogeneous particle density in the TR-region; (ii) the progressive resolution change is replaced by an abrupt transition from the AT level at the TR boundary, the buffer region now corresponding to normal AT molecules with density anomalies corrected using a similar effective one-particle force. In recent applications, the TR-AdResS scheme has also been used to handle non-equilibrium situations or to bridge atomistic systems with continuum hydrodynamic reservoirs. Adaptive-resolution schemes relying on a buffer layer with FG↔CG solvent interconversion (as well as the closely related mixed-resolution schemes) have three main shortcomings 82 : (i) for a given choice of solvent, they rely on a unique graining level N G that must be selected prior to the design of a CG model; (ii) this CG model must be parametrized, which is a non-trivial task, or an existing model must be taken from the literature; and (iii) the imperfect compatibility between the FG and CG models generally induces boundary artifacts. The latter artifacts can be eliminated by application of different types of corrections, including a biasing of the chemical potential or the application of a thermodynamic force along the density gradient. Note that AdResS can also be used in a grand-canonical fashion, where the CG model is replaced by non-interacting tracer particles. In a recent article, we introduced a simple and elegant approach to derive CG models of arbitrary graining levels directly based on a given FG solvent model. The mapping involves a scaling of the spatial dimensions by a factor s, with the FG model corresponding to an s-value of one, along with a corresponding s-dependent adjustment of the force-field parameters of the solvent molecule. The latter changes are designed to achieve an isomorphism between the dynamics of the FG and CG models, and to preserve the dispersive and dielectric solvation properties of the solvent with respect to a solute at FG resolution. For a given value of s, the CG model thus represents a "blown up" version of the FG model with a graining level N G = s 3 . It involves the same number N S of interaction sites in the same angular geometry, but different bond lengths as well as different atomic masses and interaction parameters. Note that a "blown-up" water-like aspect has also been selected empirically in a number of existing three-site CG water models .