Modern people are in a vast ocean of information. According to estimates, since the beginning of the 20th century, human knowledge has doubled every 10 years; in the 1970s, it doubled every five years, and now it has doubled every two to three years. With such a wealth of information and new knowledge, it is impossible and unnecessary to rely solely on your own brain to store memories. Smart learners know how to use their "external brain" to store all the knowledge they need and build their own "external brain information library." This "external brain information database" includes not only various ready-made books and periodicals, but also other people's experiences and lessons and collective wisdom.