633 Address all correspondence to Trefor Evans, tevans@triprinceton.org Preface TREFOR A. EVANS Director of Research and Institute Fellow, TRI Princeton, Princeton, New Jersey, USA (T.E.) Chairman of 9th International Conference on Applied Hair Science The International Conference on Applied Hair Science is organized by Textile Research Institute (TRI) Princeton every other year with the goal of bringing together hair scientists and researchers from around the globe to share findings, ideas, and discoveries. The ninth iteration of this event was originally scheduled for June 2020 in Red Bank, New Jersey, but the Covid health crisis led to postponement until June 7–11, 2021, and the implementation of a virtual format. This new medium allowed a considerably wider audience to be reached, and more than 1,000 hair scientists from all around the world registered for this online event. The program consisted of 24 presentations by speakers from seven different countries. A poster session attracted a further 17 submissions. Presentations were slotted into four sessions dedicated to Hair Biology, Insights into Hair Structure, Hair Insults and Protection, and New Methods. All lectures were recorded so they could be viewed “live” and/or later “on demand” by conference attendees. This special edition of Journal of Cosmetic Science features nine articles based on talks presented at this conference and includes submissions from each of the four sessions. These papers illustrate the diversity of the event by describing work in the areas of hair biology, hair structure, chemical composition, measurement science, and formulation science. Similarly, articles were penned by a variety of authors from academia, end-product companies, ingredient suppliers, and testing laboratories. TRI thanks everyone who helped make the 9th International Conference on Applied Hair Science a resounding success. This includes the organizing committee, sponsors, presenters, and participants. See you all in 2022! J. Cosmet. Sci., 72, 633 (November/December 2021)