Mihaly Csikszentmihalyi is a Hungarian-American psychologist best known for his work on the concept of flow. He defined flow as a state of complete immersion and engagement in an activity, where individuals experience heightened focus and enjoyment. His research has influenced various fields, including psychology, education, and sports. Csikszentmihalyi's book, Flow: The Psychology of Optimal Experience, published in 1990, outlines the conditions necessary for achieving this state. He emphasizes the importance of balancing challenges and skills to foster creativity and personal growth, making his ideas relevant to both personal development and professional environments.