Do you know that cholesterol is very abundantly distributed in the brain? Unexpectedly, it is not sufficiently known that the brain is an organ owning high level content of cholesterol. Cholesterol is also widely distributed in the blood as lipoproteins such as HDL and LDL. Surprisingly, cholesterol accounts for as much as 25% of total body cholesterol in human brain. Why is cholesterol distributed abundantly in the brain? What is the role of cholesterol in the brain? This book describes the role of astrocytes in brain cholesterol homeostasis and the relationship between cholesterol homeostasis and brain disorders.