Single-particle imaging (SPI) using X-ray Free Electron Lasers (XFEL)provides a promising approach for structural determination of macromoleculesat ultrafast timescales. A key challenge in SPI is the precise aerosolizationand injection of particles into the XFEL beam to maximize hit rateswhile minimizing background noise. This study explores the use of Rayleighscattering microscopy as a tool for tracking and sizing aerosolized particles,optimizing their delivery for high-resolution imaging experiments.By employing an electrospray-based injection system and analyzing scatteredlight intensity, we demonstrate the feasibility of particle characterizationwithout requiring a full XFEL setup. Calibration using polystyrenespheres of known sizes enables accurate size determination of unknown samples.The resulting size distributions, validated against a Differential MobilityAnalyzer (DMA), confirm the reliability of this approach. Furthermore,comparative studies on Bacteriophage MS2 reinforce the applicabilityof Rayleigh scattering for biological sample analysis.The findings of this work contribute to refining aerosol delivery techniquesin SPI, improving particle focusing and injection efficiency. This methodoffers a cost-effective and iterative approach for enhancing sample delivery,paving the way for more precise and reproducible single-particle diffractionexperiments. Future developments could extend its application to studyingdynamic biomolecular processes and optimizing experimental conditions forhigh-resolution imaging.