One of the important frontiers of biology of the 21^st century will be the analysis of the atomic structure of biological macromolecules as well as the conformational changes of these structures, which implies changes in biological function. Theoretical studies pioneered by Janos Hajdu and co-workers predict that with an ultra-short, ultra-intense coherent X-ray pulses it may be possible to record a diffraction image of a macromolecule in a single shot, without the need for crystallization. To make this feasible, the photon flux and duration of the X-ray pulse must fulfill stringent requirements. A high photon flux is required to be able to collect a sufficient number of diffracted photons for forming an image. The pulse duration must be short enough to prevent the molecule from disintegrating before the diffraction is over. These conditions call for some 10^{12} – 10^{13} X-ray photons (at a wavelength of about 0.1 nanometer) to be delivered within a pulse of a few femtoseconds in duration. With these X-ray pulses copies of reproducible samples can be diffraction imaged at different orientations, from which the full three-dimensional architecture of the particle can be obtained.

This prospect of single-molecule imaging has provided the main motivation for building the large-scale, accelerator-based X-ray free electron lasers at Stanford, USA, and at Hamburg, Germany. The shorter the X-ray flash, the closer the molecule retains its original structure during exposure, see figure. Hence, the few-femtosecond, brilliant X-ray pulses being pursued with LAP’s state-of-the-art ultra-intense lasers will provide ideal prerequisites for single-specimen diffraction imaging. The potential for breaking new grounds in science and technology is great, with impacts in all areas where structural information at or near atomic resolution is valuable.