First, the most important experimental techniques are briefly reviewed, including the diamond anvil cell (DAC) technique. As a first example, it is demonstrated that carefully selected type III carbon dioxide binaries exhibiting gas-gas-like fluid phase behavior can be combined to give a ternary system, which might show large cosolvency effects and, as a consequence, two-phase holes in the three-phase liquid-liquid-gas sm face and/or one-phase miscibility windows surrounded by heterogeneous states (e.g., carbon dioxide + 1-decanol + tetradecane). As a second example, type VI binary systems exhibiting closed immiscibility loops in isobaric temperature (composition) diagrams are considered. With increasing pressure, such closed loops can shrink or even disappear completely (e.g., tetrahydrofuran + water); have a tube-like shape, often with a narrowing at medium pressures (e.g., 3-aminopentane + water); or even appear at high pressures only (so-called "high-pressure immiscibility", e.g., tetra-n-butylammonium bromide + water). Finally, isopycnic and barotropic effects are discussed in relation to the phenomena described above.