Polymer stabilized lipid nanodiscs offer enormous potential as tools for enabling membrane protein structural studies & biophysics. Polymer stabilized lipid bilayer discs are easily made by adding polymer to a suspension of lipids or disrupted cell membranes, with discs forming within ~5 minutes. It is not clear how the polymer forms discs from these systems, since in vesicles or cell membranes the headgroups are exposed to solution, and the soluble polymer, but in the final discs, the polymer is wrapped around the tail regions of the lipid bilayer. We have also observed that nanodiscs are dynamic, and undergo exchange of lipids between discs or between discs and lipid bilayers on ~10 min timescales. Here we propose to use stop-flow on Sans2d to study nanodisc formation from a solution of vesicles mixed with polymer, and also to probe the kinetics of lipid exchange between nanodiscs.