1/256, quality metrics show the virus electron density determined using *ab initio* phasing is of almost the same quality as the high signal data. This suggests that given sufficient number of single particle diffraction patterns from sub-10 nm biomolecules with current XFEL parameters (assuming a proportionate reduction in instrument background), or from 60-nm viruses with a pulse 256 times weaker, one can obtain reliable 3D electron densities with the methods presented here. In order to obtain higher resolution, many more patterns will be required to achieve sufficient statistics. This may soon be within reach with advancements in sample delivery methods as well as with high-repetition-rate XFEL sources such as the European XFEL and LCLS-II.

\[sec:experiment\]Experiment description
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Diffraction snapshots of aerosolized PR772 viruses were collected at the Linac Coherent Light Source (LCLS) as described in [@Reddy:2017]. Briefly, diffraction patterns were recorded on a pnCCD detector in the AMO instrument at the LCLS [@Ferguson:2015] at a photon energy of with the detector placed downstream from the X-ray-sample interaction point, giving a resolution of at the center-edge of the detector and maximum resolution of in the corner of the detector. This data set is available for download from the Coherent X-ray Imaging 