Although many other detection methods are still in use, optical technology has represented a key innovation in automated hematology analysis since its introduction. Light, scattered and detected at specific angles, captures an array of information about cell size, structure, inner complexity, nuclear segmentation and cytoplasmic granulation. As an innovative expansion of optical flow cytometry, Multi-Angle Polarized Scatter Separation (MAPSS™) technology (Abbott Diagnostics, Hematology, Santa Clara, CA, USA) uses four different light scatter signals to characterize distinct cellular features for the identification of various blood cells. MAPSS™ technology reliably automates WBC differentials, and continues to be improved and expanded upon. The MAPSS™ and advanced MAPSS™ technology that are integrated in Abbott hematology analyzers enable clinical laboratories to obtain high quality results.