Harold D. Lasswell was an influential American political scientist and communication theorist, born on February 13, 1902. He is best known for his work in the fields of political psychology and propaganda. Lasswell developed the famous phrase "Who says what in which channel to whom with what effect?" to analyze communication processes and their impact on society. Lasswell's contributions extended to the study of public opinion and the role of media in politics. He served as a professor at various universities and published numerous works, including Propaganda Technique in the World War and Politics: Who Gets What, When, How. His ideas continue to shape the understanding of communication and political behavior today.