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.
Friendship rings can be worn on anything finger, including the thumb, except that left ring finger. Promise for Marriage or Abstinence As for a pre-engagement ring, fidelity/monogamy, and purity rings, those are typically worn on the left ring finger. Once you are married or officially engaged, they are typically replaced with your wedding rings.