X-ray computed tomography (CT) is a power-full 3D imaging technique for the in-situ and non-destructive investigation of the inner structure of an object. This relatively recent technique has tremendously evolved over the past decade with much more sensitive detec-tion systems and increased spatial resolution. Indeed it is now possible to reach spatial res-olution of tens of nanometers with synchro-tron X-ray source but also with lab-based systems (called nano-CT). Reaching such high spatial resolution made CT a valuable technique for the 3D detection and location of nanomaterials, their aggregates and agglomer-ates (NOAA) in manufactured materials (wood coating, polymers ..) and in complex and/or natural media (plants, organisms, or-gans …). The Nano-ID1 platform, installed at CEREGE (Aix en Provence, France), is equipped with two CT systems and offers the opportunity to perform multi-scale analysis on a same sam-ple, i.e. 3D imaging with a spatial resolution ranging from 50 µm to 50 nm. For example, in a study focusing on the aging of wood-coating containing CeO2 nanomateri-als and associated NOAA released, multi-scale micro and nano-CT gave the keys to identify NOAA distribution in non-aged mate-rials and their behavior during aging. In the field of “safer-by-design” production or eco-conception, the accurate distribution of NOAA and their residues in complex matrix-es is of particular interest to understand the the consumers and environmental exposure. We also demonstrated the relevance of multi-scale micro-CT (down to submicron-scale) to detect and locate CeO2-based NOAA within soft tissues (e.g. mouse lung tissues) after in vivo exposure and artefact-reduced sample preparation procedure. This capability is gaining interest especially since the scientific community cautiously address the potential risk of NOAA for humans and living organisms.