JC-1 stained mitochondria in sperm midpieces illuminate sperm that glide over the endometrial surface 5 min after the addition of the sperm to a preovulatory endometrial explant. Sperm can be seen stopping at the openings of two glands that are side by side at the left side and center of the video. This was due to the binding of the heads to the epithelial surface of the funnel-shaped entrance of the glands (Fig. 1C). The fluorescence video was taken using BZ-X TexasRed (OP-87765) filter set and then converted to gray scale using ImageJ (version 1.51j8). The video (http://movie-usa.glencoesoftware.com/video/10.1530/REP-19-0414/video-1) from the online version of the article is available at https://doi.org/10.1530/REP-19-0414.