The Alzheimer's Disease Neuroimaging Initiative 3 (ADNI3) is a study aimed at understanding Alzheimer's disease (AD) better. It looks at various factors such as clinical symptoms, memory, brain imaging, genetics, and chemicals in the body to learn about Alzheimer's from normal aging to dementia (a severe decline in memory and thinking skills). The study does not involve any treatments but gathers information to help future research. **Key Points:** - **Participation Duration**: Up to 5 years with various tests including brain scans and memory assessments. - **Eligibility**: Open to adults aged 55-90, including those with normal cognition, mild cognitive impairment (MCI), or mild AD. - **Participation Requirements**: Includes visits for tests, providing blood samples, and possibly spinal fluid samples. This study is important for those interested in contributing to Alzheimer's research without undergoing treatment. Participants will help advance understanding of the disease, which may eventually lead to better treatments or prevention strategies.