Simplify the following text for a Grade 12 native English-speaking person.
Original: An accurate theory of electromagnetism , known as classical electromagnetism , was developed by various physicists over the course of the 19th century , culminating in the work of James Clerk Maxwell , who unified the preceding developments into a single theory and discovered the electromagnetic nature of light .
Simplified: Many physicists then developed a theory of electromagnetism now known as classical electromagnetism . James Clerk Maxwell then brought everything together into one theory of electromagnetism .