Imagine if your body could send out warning signals before you even feel ill. No pain, fever, or obvious symptoms, yet at a biological level, something may already be changing. New research suggests that exposure to harmful substances can sometimes be detected much earlier than previously thought — not through visible symptoms, but through subtle changes in how our genes are regulated. By learning how to read these early signals, scientists hope to improve prevention, protect people in high-risk workplaces, and act before health problems develop.