Lipids are usually the forgotten players in the equation that connects genotype with phenotype, despite the important roles they play in cell metabolism. Certainly, it is now commonly accepted that they are involved in all main metabolic processes of the cell: they are the main constituents of the cell membranes, but they are also involved in apoptosis, cell signaling… etc. Every cell (sub) type has a well-defined, strictly regulated lipidome, which is maintained among individuals. Even subtle variations in the metabolic status of a cell involve modifications of the lipid expression and therefore, the lipid signature of a cell or tissue may serve to identify the early onset of a disease, in addition to give important insights into its metabolic basis. However, lipid analysis is complex and it is usually carried out in homogenates that only enable extraction of an average lipid signature of a sample.

In this context, lipid imaging mass spectrometry (LIMS) emerges as a label-free technique able to map lipids with cellular resolution. In some sense, LIMS can be envisioned as a new molecular histology technique that enables visualization of tissue sections from a metabolic point of view. In this seminar, we will present several examples to illustrate the potential of this technique, and what it adds to the study of the pathological state.