Answer:
He proposed that matter can be converted to energy and vice versa .
Step-by-step explanation:
Albert Einstein gave the theory that matter can be converted to energy and energy can be converted to matter . Another name given to it is mass energy equivalence .
That means energy can be converted to matter and matter can also be converted to energy .This is the summary of the Special theory of relativity.
Examples that are very clear about matter to energy conversion are numerous in chemisal or nuclear reactions.
When the temperature of an object is increased, experiments proved that there will be a slight variation of the mass of that object .