With the upcome of shorter and shorter time scales, time dependence of multiple diffraction effects will play a fundamental role in X-ray optics. Here we report on experimental X-ray photon storage in backscattering geometry between two silicon crystal slices cut from a monolithic ingot. The slices are 150 mm apart and wedge shaped to vary the diffracting thickness between 50 μm and 500 μm. A photon energy of 15.816 keV fulfills the condition for the 888 Bragg reflection. We used the dedicated backscattering beamline ID28 at ESRF which delivers a highly monochromatic beam equal to the natural width of the reflection considered. In Bragg condition, each crystalline boundary of the cavity has a probability of photon transmission and reflection, the ratio depending on the crystal thickness. Once a photon is transmitted by the first slice, it can be reflected by the second crystal and so on. A fast avalanche detector positioned behind the cavity detects the photons as a function of time with respect to the synchrotron bunches. Thus, photons that exit inc direct transmission, or after N multiple forth and back bounces are separated by N time one nanosecond. Up to 14 reflections could be observed. The experiment demonstrates not only feasibility of photon storage in a crystal cavity which may be relevant in the X-ray optics for a free electron laser but it also points towards the importance of the time domain, where pulses shorter than the diffracting volume may be deformed and shaped considerably due to multiple scattering.