The Diamond Age of Cytometry: From Fulwyler to Spectral Multiplexing

Over the past 6 decades, cytometry has evolved from a niche experimental method into a cornerstone of modern biomedical research. The development of the first cell sorter by Mack Fulwyler laid the groundwork for technologies that now define single-cell analysis. From the early challenges of instrument operation and laser alignment to today's era of automated, high-parameter systems, the field has undergone continual transformation. We now enter what may be termed the "diamond age" of cytometry, an era of exceptional sensitivity, resolution, and analytical depth, driven by innovations such as spectral flow cytometry. Here, we reflect on the historical milestones that shaped the discipline, the cultural and educational shifts within the community, and the future challenges of standardization and quantitative rigor.