This section provides practical knowledge about the molecular structures, clinical use conditions, and laboratory applications of biomarkers, focusing on those currently in use, soon to be used, and those with high potential. Main biomarkers for AD diagnosis include Aβ fragments, tau protein forms, neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), and alpha-synuclein (αSyn). Aβ fragments, central to AD pathology, are released by the cleavage of amyloid-beta precursor protein (APP). They form amyloid plaques and can be detected in cerebrospinal fluid (CSF) and plasma, with specific ratios aiding in diagnosis. Tau proteins, particularly phosphorylated tau (p-tau) and total tau (t-tau), reflect neurofibrillary tangles and neurodegeneration. NfL, a marker of axonal damage, and GFAP, indicative of reactive astrogliosis, are measured in CSF and blood. αSyn, associated with synucleinopathies, forms aggregates detectable in biological samples. Detection methods include conventional immunodetection techniques like ELISA, ultrasensitive technologies like SIMOA, and amyloid seed amplification assays (SAA). These methods enable the accurate measurement of biomarkers, enhancing early diagnosis and monitoring of AD.