The correct answer is amygdala
The amygdala is part of the so-called deep brain, in which basic emotions, such as anger or fear, and survival instinct prevail. Basic, no doubt, for the evolution of any kind. The amygdala, this almond-shaped structure, is characteristic of all vertebrates and is located in the depth of the temporal lobes, being part of the limbic system and processing everything related to our emotional reactions.
In neurobiology it is almost impossible to associate a single emotion or function with any structure, but when we speak of the amygdala, we can say without being mistaken that it is one of the most important ones associated with the world of emotions. It is what makes us, for example, more malleable than any close evolutionary relative, it is what allows us to escape from situations of risk or danger, but it is also what forces us to remember our childhood traumas and all that made us suffer at some point.