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.
In Sinhala and Tamil culture, the groom wears the wedding ring on his right hand and bride wears it on her left hand ring finger. This can be seen in countries like Sri Lanka where there is a rich Sinhala and Tamil cultural influence in the society.