Biomarkers are central to personalized medicine by enabling accurate diagnosis, prognostic evaluation, and patient stratification for optimized therapy. Their clinical utility requires rigorous performance assessment, which encompasses analytical validity, clinical performance, and scientific evidence. Regulatory frameworks, including the EU In Vitro Diagnostic Regulation (IVDR), EN ISO 14155, and ISO 20916, establish internationally harmonized standards for safety, quality, and ethical conduct of clinical performance studies. Human biological materials—such as serum, plasma, urine, and saliva—are indispensable for diagnostic research and must be collected, processed, and stored under standardized preanalytical conditions (e.g., SPREC coding) to ensure reliability. Ethical oversight, informed consent, data protection, and the role of ethics committees remain essential safeguards, especially in studies involving vulnerable populations. Biobanks, supported by quality standards like ISO 20387, play an increasingly critical role by providing high-quality biomaterials and enabling long-term research. Together, these scientific, regulatory, and ethical frameworks form the foundation for advancing biomarker discovery, ensuring patient safety, and driving innovation in in vitro diagnostics.