For much of the 20th century, the prevailing view in biology held that an organism's genetic sequence, the specific order of DNA, was essentially fixed at birth and remained the sole determinant of how genes would be expressed throughout an individual's lifetime. The emerging field of epigenetics has significantly complicated this once-straightforward picture. Epigenetic mechanisms involve chemical modifications that attach to DNA or its associated proteins without altering the underlying genetic sequence itself, yet these modifications can still switch specific genes on or off, effectively altering how that genetic information is expressed. Crucially, environmental factors, including diet, stress levels, exposure to toxins, and even certain early-life experiences, have all been shown to influence these epigenetic modifications. Perhaps most strikingly, some research suggests that certain epigenetic changes can be passed on to subsequent generations, a phenomenon that appears to challenge the traditional assumption that only DNA sequence itself is heritable. Studies involving certain rodent populations, for instance, have found that stress or nutritional experiences of parents can measurably affect the physiology and behaviour of their offspring, even when the offspring themselves were never directly exposed to the original stressor. This research remains an active and sometimes contested area of study, since determining precisely how significant these transgenerational effects are in humans, given the many confounding social and behavioural factors involved, presents considerable scientific and methodological challenges. Nonetheless, epigenetics has fundamentally reshaped how scientists think about the relationship between genes, environment, and inherited traits.