The researchers looked for features including chemical tweaks to DNA that prime genes to be switched on or off, and alterations to the 'histone' proteins around which DNA is wrapped. Chemical or structural modifications to histones can affect which genes the cellular machinery translates into proteins and which remain silent. Such epigenetic changes can dramatically affect a cell’s behaviour and function.

The epigenomes also contain hints of how epigenetic changes could be involved in diseases, including cancer, Alzheimer's disease and autoimmune diseases.

Taken together, the work demonstrates how a cell’s epigenome is complex and exquisitely arranged — just like a Beethoven symphony.