One of the most fascinating aspects of molecular and cellular biology is the ability of a zygote to develop into diverse cell types during development. Each of these cell types, despite containing identical genetic material, possesses highly specialized functions, showing that this difference must have a non-genetic basis. This is globally referred to as epigenetics that can be defined as gene regulatory systems affecting gene expression independent of DNA sequence.

Gene expression regulation by epigenetics can occur in several forms, from transcription to translation. While small noncoding RNAs posttranscriptionally and translationally act on mRNAs, transcriptional epigenetic regulations are chromatin-based and can be encoded by histones and their chemical posttranslational modifications (PTMs). For example, the methylation of histone H3 at position lysine 27 (H3K27me) is a facultative heterochromatin mark that plays a key role in cell differentiation. H3K27me3 PTMs decorate the chromatin and create an epigenetic memory that can be transmitted from parents to zygotes to the germ line of developing animals. Perturbation of its inheritance results in development and fertility defects in different species, underlying the importance of epigenetic inheritance (EI) of H3K27me3 genomic patterns. However, we have a limited understanding of the principles and mechanisms of the H3K27me3 inheritance. Currently, the biggest challenge to studying the inheritance of H3K27me3 is the absence of a tractable experimental setup for genetic and molecular investigations in vivo.