(a) Snapshot XFEL transmission X-ray diffraction pattern from PS I. This is a single pulse of 70 fs duration, with 2 mJ of 1.8 kV X-rays at 0.688 nm wavelength. The resolution is 8.9 Å at the corner. Blank areas are faulty detector panels. The beam diameter was 7 µm and this single pulse contained about 1012 photons. [See Chapman et al. (2011) for details.] (b) Recorded under similar conditions to (a), but using a smaller camera length for higher angular resolution of low orders. This snapshot pattern from one protein nanocrystal shows the Fourier transform of the needle-shaped nanocrystals laid down around reciprocal-lattice sites. The number of subsidiary maxima between Bragg reflections shows that there are 19 periods of the crystal running between facets along the diagonal direction of the fine fringes. The vertical streak is diffraction from the column of liquid water in which the nanocrystals run [see Spence et al. (2012) for details].