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 first option is to wear them on the traditional ring finger, on your left hand, in the order your received them in. This means the diamond ring goes on bottom, and the wedding band on top. This is a traditional way of wearing the rings, but may not work with all ring styles or finger types. Keeping with tradition, you can wear both rings on the left hand on the ring finger, but with the engagement ring on top.