Various categories of heterochromatin exist and are regulated by different proteins, RNAs, and mechanisms to restrict the access of transcription factors in different ways and degrees.Activation of a gene during reprogramming that was in heterochromatin requires the opening of the heterochromatin and the activating factors.Disruptive mechanisms required for maintenance of heterochromatin make sites receptive to the binding and activation of transcription factors, but can activate off-target genes and repeat elements. Heterochromatin is defined as a chromosomal domain harboring repressive H3K9me2/3 or H3K27me3 histone modifications and relevant factors that physically compact the chromatin. Heterochromatin can restrict where transcription factors bind, providing a barrier to gene activation and changes in cell identity. While heterochromatin thus helps maintain cell differentiation, it presents a barrier to overcome during efforts to reprogram cells for biomedical purposes. Recent findings have revealed complexity in the composition and regulation of heterochromatin, and shown that transiently disrupting the machinery of heterochromatin can enhance reprogramming. Here, we discuss how heterochromatin is established and maintained during development, and how our growing understanding of the mechanisms regulating H3K9me3 heterochromatin can be leveraged to improve our ability to direct changes in cell identity.