Horny Goat Weed is an ornamental plant that also has a long history of traditional use in Chinese herbalism. In China, Horny Goat Weed is called yin yang huo because it is a tonic for the female (yin) and the male (yang). Epimedium was thought to “tonify life’s gate” – a term used to refer to the “vital energy” in men. NOW® Horny Goat Weed Extract is combined with Maca, another herb known for its tonifying properties.