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.
The left hand ring finger, which is the one next to the pinkie finger. You wear the engagement ring there until the day of the ceremony, when you either move it to the right hand or put it somewhere safe so your new husband can place the wedding band on the left ring finger. After the ceremony, you put the engagement ring back, so that it is next to the wedding band. The band is traditionally put on first, then the engagement ring, because the band is supposed to be closer to your heart. The tradition of using the left hand is an old one.