To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video Video 1 Stained human spermatazoa showing the movement of the large extra-mitochondrial formazan deposit in an anterior direction. This video (http://movie-usa.glencoesoftware.com/video/10.1530/REP-20-0205/video-1) is available from the online version of the article at https://doi.org/10.1530/REP-20-0205. Patterns of MTT reduction in mammalian spermatozoa Robert John Aitken, Diatsendoula Gregoratos, Leslie Kutzera, Emma Towney, Minjie Lin, Alexandra Wilkins, and Zamira Gibb 2020. 160:431-445 DOI: 10.1530/REP-20-0205 Download Original Video