X-ray or neutron diffraction experiments are the best way to determine molecular structure at a nanometer scale.

Thanks

A similar question was posted earlier

https://www.researchgate.net/post/How_can_I_calculate_bilayer_thickness_thickness_of_the_lipid_bilayer_excluding_water_for_hydrated_soy_lecithin

Article Bilayer thickness and lipid interface area in unilamellar ex...

https://link.springer.com/article/10.1007%2Fs00249-003-0349-0

thanks a lot