Theory of Computation (TOC) has undergone a number of evolutions in a short span of time. From its beginning in the 1960s as an outgrowth of mathematical logic and information theory, it evolved into a branch of mathematics where one looks at classical problems with the aesthetics of computational complexity and asks new questions concerning non-determinism, randomness, approximation, interaction, and locality. It then took a foundational role in addressing challenges arising in computer systems and networks, such as error-free communication, cryptography, routing, and search, and is now a rising force in the sciences: exact, life, and social. The TOC group at MIT has played a leadership role in theoretical computer science since its very beginning. Today, research done at the TOC group covers an unusually broad spectrum of research topics.