Molecular neuroimaging has transformed the landscape of Alzheimer’s disease (AD) research and diagnosis by enabling in vivo visualization of its core molecular hallmarks—amyloid-β plaques and tau neurofibrillary tangles. This transition has fundamentally reshaped AD as a biological continuum rather than a purely clinical syndrome, anchoring diagnosis in quantifiable biomarkers that precede cognitive decline by years or even decades. The integration among amyloid and tau positron emission tomography (PET) with magnetic resonance imaging provides complementary insights into both molecular pathology and structural or functional brain alterations, facilitating precise staging of disease progression and differential diagnosis among neurodegenerative disorders. Recent advances in tracer chemistry, digital photon detection, and artificial intelligence-driven analytics are propelling molecular imaging into the era of data-driven precision neurology. Molecular PET now functions as a diagnostic gatekeeper for disease-modifying therapies and a pharmacodynamic biomarker for evaluating treatment response in clinical trials. Yet these breakthroughs raise ethical, clinical, and social challenges, including equitable access to imaging technologies, data governance for large-scale neuroimaging repositories, and the psychological implications of disclosing preclinical biomarker status to cognitively normal individuals. Looking ahead, the convergence of molecular imaging, multimodal data integration, and computational modeling promises to establish a comprehensive model for individualized disease prediction, prevention, and therapeutic monitoring. In this emerging paradigm, molecular neuroimaging will not only illuminate the pathophysiological cascade of AD but also serve as a cornerstone of precision medicine across the broader spectrum of neurodegenerative diseases.