Novel insights into mechanisms of endothelial dysfunction (impaired flow-mediated dilation, FMD) induced by electronic cigarette aerosol exposure (acute pathway: rats) and chronic use (chronic pathway: human E-cig users) as revealed in the complementary studies in this issue of ATVB (#, pgs). Abbreviations: AA, acetaldehyde, PG:G, propylene glycol:glycerin; RAGE, receptor of advanced glycation endproducts.