Other than normal and abnormal psychology and behavior on an individual level, and interpersonal behavior on a grander scale, my favorite aspect of psychology is drugs.
I think it is the most interesting ever to learn about different kinds of drugs and their effect on individuals and societies. I love learning about different chemicals in the body and how certain foods and drugs can release those chemicals and cause both individuals and interactions among relationships with loved ones and strangers are so strongly effected.
They can make you happy, sad, scared, excited, nervous. they can end the pain or make you feel intense feelings of emotions you never knew you had the potential to inside of you. They can make you see things or hear things that arent there, and do things without knowing why. They can make you think crazy things for which there is absolutely no rational foundation, and can significantly affect your interactions with anyone and everyone in the world in both positive and negative ways.
And, with the right amounts, they can either save human lives or end human lives.
Drugs are like magic, heavily influencing the human body, mind, and interaction, and life, and that is why they continue to be a topic of such extreme fascination to me to this very day.