Measuring just 5 µm in internal diameter, the ultra-fine blood vessels called capillaries are known to play an important role in supplying oxygen and nutrients to cells and tissues. As we age, our capillaries become even finer and sparser. Once they enter this state, becoming what are called “ghost vessels”, the blood flow through the capillaries declines and they become unable to transport oxygen and nutrients. As a result, the cells and tissues around the ghost vessels gradually become damaged and their function deteriorates. The latest research has identified a relationship between these ghost vessels and a variety of diseases, including lifestyle-related diseases such as diabetes and hypertension.