(a) Serial femtosecond X-ray diffraction (SFX) with one protein microcrystal per shot. (b) Fast solution scattering (FSS) with many similar molecules per shot. (c) The single-particle (SP) mode with one particle per shot. (d) A mixing jet for snapshot imaging of slow dynamics. (e) shows a simple Rayleigh jet, in which the water stream breaks up into perfectly spherical droplets a few micrometres in diameter (Weierstall et al., 2008). Fixed-sample stages are also used (see text). All these may be combined with X-ray absorption or emission spectroscopy.