In this lecture I present simulations, using the Martini coarse-grained model, exploring ternary raft-mimicking lipid mixtures, composed of saturated and unsaturated lipids together with cholesterol. I will show the spontaneous formation of liquid-disordered and liquid-ordered membrane domains in agreement with experimental findings. The question whether a fourth component such as a lysolipid could act as a lineactant, stabilizing the domain boundary, will also be explored. Simulations of the addition of model membrane proteins furthermore reveal the preferential partitioning of these peptides into the liquid-disordered phase, regardless of the hydrophobic mismatch. Free energy calculations reveal the driving forces giving rise to this sorting effect.