Final answer:
Nuclear processes, such as those in nuclear power plants and nuclear weapons, represent 100% mass to energy conversion. This conversion is governed by the mass-energy equivalence equation, E = mc², derived from the theory of special relativity by Albert Einstein.
Step-by-step explanation:
The process that represents 100% mass to energy conversion is nuclear processes, specifically in nuclear power plants and nuclear weapons. In these processes, a small amount of mass is destroyed and converted into energy, which is released in the form of nuclear radiation. This conversion is governed by the mass-energy equivalence equation, E = mc², as derived from the theory of special relativity by Albert Einstein.