Audio Guide：

Scientists hold that the universe is made of regular matter, regular energy, dark matter, and dark energy. Regular matter includes protons, neutrons, electrons, and everything they constitute, like our bodies and the stars—all of that only makes up about 5% of the total universe. Dark matter is undetectable by electromagnetic instruments, but it still possesses a huge force—it makes up 27% of the universe. Dark energy has unknown characteristics, but we know that it is the reason that the universe is expanding at an increasing speed—that makes up the remaining 68%.