Library is good; it solves the problem in a minute. Someday, Adafruit or other respected individuals might discontinue the supplies of the Library Functions. Therefore, based on Arduino's basic functions (like Wire.beginTransmission(), Wire.write(), Wire.endTransmission(), Wire.requestFrom(), Wire.read()), we may try writing our own codes standing on one level lower platform. This way, we may slowly acquire the ability of writing Register Level instructions that might open opportunity to understand the 'System'.