While he wasn't the first to propose this idea, he developed it extensively in his work, "Opticks," published in 1704. He called these particles corpuscles.
However, this corpuscular theory of light was later challenged by Christian Huygens who proposed the wave theory of light, suggesting that light traveled in waves. This debate continued for centuries until the development of quantum mechanics in the early 20th century, which ultimately showed that light exhibits both wave-like and particle-like properties.
