This proposal is the first part of a fundamental study aiming to improve understanding about technically challenging water-in-CO2 (w/c) microemulsions, by firstly investigating proxy systems which can be more readily probed under laboratory conditions. The ¿surfactant film bending energy theory¿ has been proved very useful for understanding normal liquid microemulsions [e.g. 1-8], for it allows to correlate optimal surfactant chain length with phase stability. This theory will be tested with high-pressure w/c systems, but before that can be done reliably it is necessary to scope the feasibility in parallel water-in-oil (w/o) liquid systems. Importantly, the contrast of the external oil phases (and in certain cases the internal water droplets) will be adjusted by D/H solvent mixing to mimic that of dense liquid/supercritical CO2 (e.g. ρsolv, CO2=1.76×10-6Å-2, at certain T and P).