Modifications in biomacromolecules (DNA, RNA, and proteins) are important molecular events in different pathophysiological conditions. These modifications include DNA modifications, RNA post-transcriptional modifications, and protein post-translational modifications that regulate the structures and functions of biomacromolecules and even the entire biological system. In addition, they are associated with a wide spectrum of diseases. Biomacromolecular modifications are important factors in creating proteoforms that constitute the end-point structural and functional forms of a gene or protein that can be applied for predictive, preventive, and personalized medicine (PPPM) as well as precision medicine (PM).