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 common in Germany and Netherlands to do the opposite: that is, to wear engagement rings on the left hand and wedding rings on the right. In the Jewish tradition, the groom slips the ring on the index finger of the bride because it is the most prominent finger.