This is Abraham Maslow.
He is considered one of the most important psychologists of the 20th century because of his association with the famous hierarchy of human needs.
This hierarchy depicts the idea that human needs can be categorized into different tiers. Tier one includes physiological needs, tier two includes safety needs, tier three includes belonging and love needs, tier four includes esteem needs, and the final tier includes self-actualization.
An interesting fact, however, is that Maslow never really used the term hierarchy to explain his theory. He merely suggested that there is a causality between lower tier needs and higher tier needs by virtue of prepotency. Most probably, the pyramid was an illustration designed by one of his publishers in order to offer to the reader a more visual representation of Maslow’s ideas.
article via: The Quintessential Mind