Epigenome, a record of the chemical changes to the DNA and histone proteins of an organism, is dynamically altered by environmental conditions and thus contributes to an adaptive mechanism for the given environmental stress. Among them, the cold environment is life-threatening to homeothermic animals. To combat, they induce thermogenic gene expression such as Ucp1 against cold stress. We recently revealed dual roles for the histone demethylase JMJD1A as a mediator of both acute and chronic thermogenic responses to cold stress, in two distinct thermogenic tissues, and through two distinct molecular mechanisms.