The discovery of biomarkers has revolutionized the field of oncology, providing critical insights into the processes of tumour initiation and progression. Biomarkers, which can be genetic, proteomic, or metabolic in nature, serve as vital indicators for early cancer detection, prognosis, and personalized treatment strategies. Tumour initiation undergoes various stages characterized by alterations in the tumour microenvironment, angiogenesis, and ultimately metastasis. Understanding these processes at the molecular level is crucial for identifying reliable biomarkers. Recent advances in high-throughput technologies such as next-generation sequencing, mass spectrometry, and advanced imaging techniques have significantly enhanced the ability to discover and validate new biomarkers. Despite the promising advancements, challenges remain in the translation of biomarker discoveries into clinical practice. This chapter provides a detailed current state of biomarker discovery, highlighting key findings and future directions in this rapidly evolving field.