Aging is the process of growing older. It is a risk factor for most prevalent neurodegenerative diseases, such as mild cognitive impairment, dementias involving Alzheimer's disease, cerebrovascular disease, Parkinson's disease, and Lou Gehrig's disease. The brain is a complicated organ that is made up of many different types of tissue and matter. The function of various tissues in brain may be more or less susceptible to age- induced changes. The structure of brain's network is formed through anatomical connection of the neurons. The aging of brain is a complex process that begins early in life and accelerates with age, affecting everything from the subcellular to the organ level. Brain volume loss, cortical thinning, white matter degradation, loss of gyrification, and ventricular enlargement are morphological symptoms of brain aging. Neuron cell shrinking, dendritic degeneration, demyelination, small vessel disease, metabolic slowing, microglial activation, and the formation of white matter lesions are pathophysiological symptoms of brain aging. This book explores all the important aspects of ageing in the present day scenario. It will provide comprehensive knowledge to the readers.