  Obtaining 3D information from a single X-ray exposure at high-brilliance
sources, such as X-ray free-electron lasers (XFELs) [1] or diffraction-limited
storage rings [2], allows the study of fast dynamical processes in their native
environment. However, current X-ray 3D methodologies are either not compatible
with single-shot approaches because they rely on multiple exposures, such as
confocal microscopy [3, 4] and tomography [5, 6]; or they record a single
projection per pulse [7] and are therefore restricted to approximately
two-dimensional objects [8]. Here we propose and verify experimentally a novel
imaging approach named X-ray multi-projection imaging (XMPI), which
simultaneously acquires several projections without rotating the sample at
significant tomographic angles. When implemented at high-brilliance sources it
can provide volumetric information using a single pulse. Moreover, XMPI at MHz
repetition XFELs could allow a way to record 3D movies of deterministic or
stochastic natural processes in the micrometer to nanometer resolution range,
and at time scales from microseconds down to femtoseconds.
