Alzheimer’s disease (AD) is the most common cause of dementia for people over the age of 65. It is a complex neurodegenerative disease that exhibits multiple pathological changes in the brain. It is still not known what causes AD. Its main pathological characteristic is the presence of aggregates of Amyloid beta (A-beta) peptides. This increase in A-beta levels in the brain underlies the most widely accepted theory of the etiology of AD, the Amyloid Hypothesis, which proposes that A-beta deposition triggers the formation of senile plaques and neurofibrillary tangles, leading to neurodegeneration. However, many hypotheses have been proposed that attempt to explain the development and progression of AD, such as the transneuronal spread of Tau, degeneration of anatomical pathways, mitochondrial dysfunction, insufficient brain glucose, increased presence of certain metals, and exposure to infectious agents. R&D Systems offers a range of research tools to study the biological processes that underlie AD.