The combination of experimental studies in cells and in vitro reconstitution experiments, along with multiscale physics-based computer simulations, proved decisive in elucidating the molecular mechanism by which FGF2 is secreted by direct translocation across the plasma membrane. Even certain discrepancies observed between cell-based data and results from in vitro experiments were informative, spurring new concepts about the spatio-temporal organization of the FGF2 membrane translocation machinery. An example is the kinetics of FGF2 membrane translocation, which is considerably faster in intact cells compared to those observed for artificial membrane systems. While individual events of FGF2 membrane translocation were shown to occur within time intervals of 200 ms , This process was found to take place in a time range of minutes when analyzed with giant unilamellar vesicles as model systems , as illustrated in Figure . Several parameters may account for this difference such as the absence of the Na,K-ATPase in the minimal reconstitution system. Similarly, putative redox enzymes, presumably involved in forming disulfide bridges during FGF2 oligomerization in cells, are not included in the in vitro models. Another striking example is the known transbilayer lipid asymmetry of native plasma membranes absent from model membranes used in FGF2 reconstitution experiments. In particular, the exclusive localization of PI(4,5)P 2 in the inner leaflet of cellular plasma membranes is strikingly different from the symmetric distribution of PI(4,5)P 2 in giant unilamellar vesicles used in in vitro experiments.