The authors wish to thank our colleagues and collaborators in the Beckman Laser Institute and the Diffuse Optics community for their generous and passionate contributions to the development and application of these technologies, and the subjects who have graciously volunteered their time. We note in particular the bold and inspirational work of Professor Britton Chance, and Professor Enrico Gratton’s exciting introduction of the PDW conceptual framework. This work was supported by National Institutes of Health grants P41RR01192 and P41EB015890 (Laser Microbeam and Medical Program), U54-CA105480 (Network for Translational Research in Optical Imaging), U54-CA136400, R01-CA142989, NCI-2P30CA62203 (University of California, Irvine Cancer Center Support Grant), Air Force Research Laboratory Agreement Number FA9550-04-1-0101, and NCI-T32CA009054 (University of California, Irvine Institutional Training Grant). Beckman Laser Institute programmatic support from the Arnold and Mabel Beckman Foundation is gratefully acknowledged. Conflict of Interest Statement B.T., A.C., and D.C. report patents, which are owned by the University of California, that are related to the technology and analysis methods described in this tutorial. The DOI instrumentation described was constructed in a university laboratory using federal grant support. The University of California has licensed diffuse optics technologies and analysis methods to two companies Volighten, Inc., and Modulated Imaging, Inc. A.C. and B.T. are co-founders of Volighten; B.T. and D.C. are co-founders of Modulated Imaging. This research was completed without financial support of either company.