Summary: Bivalent chromatin is characterized by occupation of both activating and repressive histone modifications. Here. we develop a mathematical model that involves antagonistic histone modifications H3K4me3 and H3K27me3 to capture the key features of bivalent chromatin. Three necessary conditions for the emergence of bivalent chromatin are identified. https://www.spidertattooz.com/Powell-Mahoney-Bloody-Mary-Mix-750ml/