looks at the timeline of life. From the cognitive leaps of infancy to the emotional challenges of old age, developmental psychologists study how we change and grow. It gives us insight into the crucial "nature vs. nurture" debate—determining how much of our personality is written in our DNA and how much is sculpted by our upbringing.

Perhaps the most vital contribution of psychology is the destigmatization of mental health. For centuries, mental illness was viewed as a moral failing, a demonic possession, or a weakness of character. Psychology provided the medical and scientific framework to prove that mental health is just as biological as physical health.

Knowing the theory is useless without action. How do we weaponize psychology for better living?