The epigenome comprises markers on DNA and its accoutrements that tell molecular machinery which bits to attend to. These labels change through environment and events, sometimes passing across generations. Genetically identical mice with different epigenomic markings can differ in colour, size and morbidity. A single epigenomic tag can mean the difference between health and sickness.
Biotech companies are using epigenetic-editing techniques to change specific epigenomic tags while leaving DNA sequences untouched. Success would help sufferers of metabolic disorders and chronic viral conditions, with broader applications potentially addressing ageing-related debilities from epigenomic wear and tear. Specific exercises clearly affect the epigenome.
The difference between reality and unreality is that reality has so little to recommend it.