MALDI Mass Spectrometry Imaging (MALDI-MSI) is a two-dimensional MALDI mass spectrometric technique used to visualize the spatial distribution of a large variety of biological molecules (from small metabolites to large proteins) without extraction, purification, separation or labelling of biological samples. Since its introduction by Caprioli et al in 1997, it has become one of the most important molecular histology methods for biomarker hunting and for understanding the spatial distribution of biomolecules in various tissues. MALDI-MSI is thus ideal for complementing the expanding field of metabolomics. Despite the fact that MALDI-MSI have been very successfully applied in divers studies (even in clinical applications) its use remains far from routine, and there is still a need to adapt protocols to suit specific tissues4 or metabolites. Here we describe the methodology of MALDI-MSI with examples taken from applications in plant (Cichorium intybus) and in seashell (Mytilus edulis).