Although vacuum-based MSI techniques, including commercialized Matrix-Assisted Laser Desorption/Ionization (MALDI-MSI) and Secondary Ion Mass Spectrometry (SIMS-MSI) , render ultra-high spatial resolution in measurements, challenges (e.g., nontrivial sample preparation and complex mass spectra at low mass) need to be overcome for successful applications. In contrast, ambient-based methods generally provide relatively lower spatial resolutions, but they require little or no sample preparation and provide simpler mass spectra (e.g., fewer interfering ions and fragments) . Particularly, some of these methods, such as nanospray desorption electrospray ionization (nano-DESI) MSI and Single-probe MSI , have successfully achieved high resolutions at the single-cell level. Unfortunately, both nano-DESI and Singleprobe MSI methods are not commercially available, limiting their broad applications.