The invention provides a system and method for characterising at least part of a material comprising: a source of incident X-rays (4, 28) configured to irradiate at least part of the material; one or more detectors (300,302,312,1701,1704,1600,1607,1608,1604) adapted to detect radiation emanating from within or passing through the material as a result of the irradiation by the incident radiation (1700) and thereby produce a detection signal (313); and one or more digital processors (304-311,2000-2009) configured to process the detection signal (313) to characterise at least part of the material; wherein the one or more detectors (300,302,312,1701, 1704,1600,1607,1608,1604) and one or more digital processors (304-311,2000-2009) are configured to characterise at least part of the material by performing energy resolved photon counting X-ray transmission spectroscopy analysis.