"The so-called opening of the Heavenly Eye is the activation of one's Upper Dantian. However, depending on the level to which it is opened, there are initial opening, small achievement, great achievement, and perfection. With the initial opening of the Heavenly Eye, one can see minutely, which means being able to clearly see tiny things, as small as what is now referred to as bacteria and other extremely small organisms."
The Northern Song scientist and politician Shen Kuo once wrote a book called 'Meng Xi Bi Tan', and within it, there is a chapter titled 'Childhood Memories'. In it, he stated that he could distinguish the most minute detail, which is because he had initially opened his Heavenly Eye."