The ancient Greek philosopher Democritus (460β370 or 356 BC) was a person who loved to think about problems and was also a very good thinker.
Eating three meals a day is the most ordinary thing. However, even while eating, Democritus was pondering. As he swallowed a mouthful of soup, he thought: Salt is white and granular. Why does the soup become salty after adding just a little bit of salt? Why is every spoonful of soup I scoop up salty, and all of them equally salty?
As he strolled among the flowers, the fragrance prompted him to ponder: Why do I smell the fragrance of flowers?
As he stood alone by the small lake, watching the fish swim, he was struck by a quiet contemplation: Why are fish able to swim so freely in the water? Perhaps water is not a very dense substance, otherwise how could fish move so freely, sometimes to the east, sometimes to the west, sometimes up, sometimes down?
After much thought and reflection, Democritus finally came to a conclusion: everything in the world is composed of extremely small, invisible particles.
Democritus famously summarized his doctrine with a phrase that is now widely known: "We speak of sweet and bitter, cold and hot, color and fragrance, but in reality, only atoms and space exist." The "atoms" Democritus referred to are, in modern terms, "molecules."