Abstract: The spatial distribution of mass within an individual analyte can be imaged—in real time and with molecular-scale resolution—when it adsorbs onto a nanomechanical resonator. Each single-molecule adsorption event induces discrete, time-correlated perturbations to the modal frequencies of the device. By continuous monitoring of multiple vibrational modes, the spatial moments of mass distribution can be deduced for individual analytes, one-by-one, as they adsorb. This new method was validated for inertial imaging using both experimental multimode frequency-shift data and finite-element simulations—to analyze the inertial mass, position-of-adsorption, and the shape of individual analytes. Unlike conventional imaging, the spatial resolution of nanomechanical inertial imaging is not limited by wavelength-dependent diffraction phenomena; instead frequency fluctuation processes determine the ultimate attainable resolution. Advanced NEMS devices can provide atomic-scale resolution.