Brown adipose tissue is present in small mammals (e.g., mice) and in newborn humans. Most of it disappears in adult humans. The cells in both types of fat are called adipocytes although they differ in origin, structure, and function in the two types of tissue.
On the left hand, index finger. It's not the index finger you wear it on. Left hand, ring finger. The finger that you would wear a wedding ring on.
During the ceremony, your soon to be spouse places the wedding ring on your left hand ring finger. The custom of the third finger on your left hand being your ring finger originated in Egypt, where people believed the vein in that finger led directly to your heart.