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.
It is the same for women and men. You wear your wedding ring on the left hand, the finger next to your pinky finger. It is usually the third finger of the left hand, but there's no rule saying that it has to be that finger. In some parts of the world people wear it on their right hands, and in other parts of the world wedding rings are not worn at all.