This book reports on an attempt to understand the unity of physics. The focus is on the effort to comprehend quantum physics. "Understanding" here does not merely mean being able to practically apply the theory; in that sense, it has been understood for a long time. It means being able to articulate what one is doing when applying the theory. Understanding the unity of physics is likely a prerequisite for insight into its philosophical meaning, that is, its role in our endeavor to open ourselves to the unity of reality.