It has been said that happiness consists of happy emotions, and a satisfaction with life. This is what we classify as real happiness, and now we have a way to observe happiness objectively.

There's a part of the brain in the medial parietial lobe called the Precuneus. This part is a large chunck of grey matter, so it's not a more organ-like type of part in the brain like the Hippocampus from what I gather. Some guy named Sato found a pattern in that people who expressed more happiness, less sadness, and found meaning in life more easily had more grey matter in their Precuneus.               

Sato and his team scanned the brains of research participants with MRI. The participants then took a survey that asked how happy they are generally, how intensely they feel emotions, and how satisfied they are with their lives.

Their analysis revealed that those who scored higher on the happiness surveys had more grey matter mass in the precuneus. In other words, people who feel happiness more intensely, feel sadness less intensely, and are more able to find meaning in life have a larger precuneus.

Correlation does not mean causation. Sample size. What Questions were asked. Define happiness etc. etc.

You do realize that correlation is the only way we can understand things, right? This is especially true when it comes to neuroscience.

We don't actively conduct experiments on peoples' brains, because it's immoral to affect people in a negative way, and because we know so little, we can't risk it. The precuneus is known for it's role in making us self-aware, or self-conscious. Thing is, there are only suggestions to what brain parts do. Check out the wikipedia page for the Precuneus' functions. Every paragraph starts with "It's been suggested that..." because we aren't allowed to remove some parts of the brain and observe the change in the person, so we make intelligent guesses.