Synthetic LNPs are commonly composed of four components; an ionizable lipid, a helper lipid, cholesterol and a poly(ethylene glycol)ylated (PEG) lipid. Ionisable lipids interact electrostatically with the negatively charged mRNA facilitating its encapsulation within the LNP. The also enable endosomal escape by appropriate pKa choice. Helper lipids, such as the phospholipids distearoylphosphatidylcholine (DSPC) and dioleoylphosphatidylethanolamine (DOPE), contribute to the structural integrity and stability of LNPs. Cholesterol is incorporated into LNPs to modulate their fluidity and rigidity, enhancing particle stability and membrane fusion capabilities and also helps maintain the structural integrity of LNPs, allowing for delivery and release of mRNA into target cells. The inclusion of PEG-lipids on the LNP surface contributes to both formulation stability, and the 'stealth' properties of the nanoparticles, with longer fatty acids allowing them to circulate in the bloodstream longer and increasing the chances of reaching their target cells whilst shorter fatty acids are shed faster enabling the lipid surface to be exposed and absorb the serum proteins. Study of the structural, compositional, and functional aspects of LNPs for drug delivery has employed various analytical and imaging techniques. Cryo-EM allows for the observation of the nanoparticle morphology and internal structure, providing insights into the lipid organization, but without information on molecular identity. Small-angle neutron scattering (SANS) combined with deuteration of components at large scale facilities has been used to quantify the lipid distribution at the surface LNPs using isotopic contrast variation. Small-angle X-ray scattering (SAXS) using synchrotron sources, has been used to probe bulk phase structures. DLS is used to rapidly measure the size distribution and polydispersity index of LNPs, offering insights into their homogeneity and stability. NMR spectroscopy provides information on the molecular structure, dynamics, and interactions within LNPs. It can be used to study the composition of the lipid core, the conformation of PEG chains, and the interaction between PEG and other components of LNPs, however the structural analysis of LNPs is limited by its sensitivity. Vacuum-based surface chemical analysis techniques such as X-ray photoelectron spectroscopy (XPS) or time of flight secondary ion mass spectrometry (ToF-SIMS) have the capability to directly analysis the nanoparticle surface to describe it in elemental or molecular terms respectively. A recent study reported the possibility of evaluating the surface chemistry of lipid nanoparticles using XPS, necessitating cryogenic conditions, including the detection of PEG on the surface. Extracellular lipid vesicles can be imaged using ToF-SIMS, however the chemical information obtained from the spectra is not sufficient to identify the different component molecules. While depth profiling ToF-SIMS has previously been employed to characterize the internal structure of giant (10-30 µm) liposomes, it's application toward depth-profiling of lipid particle molecular identification at the nanoscale has not been reported. The development of OrbiSIMS addresses the limitations of ToF-SIMS in analysing high-mass biomolecules with high mass resolving power, whilst utilising gas clusters as an analysis beam provides improved detection of high molecule weight species and preserves molecular information when depth profiling.