The article discusses the application of charge detection mass spectrometry (CD-MS) and Orbitrap individual ion mass spectrometry (I²MS) for analyzing heterogeneous and high molecular weight samples. CD-MS and I²MS overcome the limitations of conventional mass spectrometry (MS) by directly measuring the mass of individual ions, allowing accurate mass measurements for samples up to giga-Daltons. The precision and resolving power of these methods are crucial for resolving complex mass distributions, particularly in the context of viruses, gene therapies, and vaccines. The article highlights the advantages of these techniques, such as the ability to resolve subpopulations and the avoidance of artifacts associated with high-resolution MS. It also provides examples of their application, including the analysis of recombinant adeno-associated virus (rAAV) gene therapy vectors and adenovirus, demonstrating their utility in characterizing complex biologics. The article concludes by discussing the potential for further improvements in mass resolving power and the broader applications of these techniques in the characterization of macromolecules, assemblies, and nanoparticles.The article discusses the application of charge detection mass spectrometry (CD-MS) and Orbitrap individual ion mass spectrometry (I²MS) for analyzing heterogeneous and high molecular weight samples. CD-MS and I²MS overcome the limitations of conventional mass spectrometry (MS) by directly measuring the mass of individual ions, allowing accurate mass measurements for samples up to giga-Daltons. The precision and resolving power of these methods are crucial for resolving complex mass distributions, particularly in the context of viruses, gene therapies, and vaccines. The article highlights the advantages of these techniques, such as the ability to resolve subpopulations and the avoidance of artifacts associated with high-resolution MS. It also provides examples of their application, including the analysis of recombinant adeno-associated virus (rAAV) gene therapy vectors and adenovirus, demonstrating their utility in characterizing complex biologics. The article concludes by discussing the potential for further improvements in mass resolving power and the broader applications of these techniques in the characterization of macromolecules, assemblies, and nanoparticles.