Many people are confronted with chronic pain that can last for months or even years. How to best treat chronic pain? First, pain must be categorized for the right treatment to be prescribed. However, is that it is very challenging for patients to define their pain, its intensity or even its location using questionnaires. To overcome this difficulty, scientists have carried out a complete epigenomic analysis of patients, making it possible to find the epigenetic signatures specific to each pain category.