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.
Some chose to use the ring finger (next to the pinky) on the right hand for the engagement and/or wedding ring because of it's resonance with, but difference from, the traditional heterosexual symbolism. Others, however, embraced the traditional practice of using the ring finger of the left hand.