Williams, Jonathan P.: - Jonathan Williams is an Astronomer at the University of Hawaii at Manoa. His research in the Interstellar Medium has ranged from the formation of the giant molecular clouds that form stars to the evolution of disks around young stars that give birth to planets. He has written pedagogical reviews on these topics and taught a wide variety of courses at the undergraduate and graduate level. This textbook builds on his course notes that have been widely used and class-tested over almost two decades.