What the Buddha saw

In a *book* I am reading it says "This is what the Buddha realized by examining himself. With his strongly concentrated mind, he penetrated deeply into his own nature and found that the entire material structure is composed of minute subatomic particles which are continuously arising and vanishing. In the snapping of a finger or the blinking of an eye, he said, each one of these particles arises and passes away many trillions of times." I don't understand how he saw this? What exactly did he see? When I meditate I dont see this. I just see thoughts.