Perpendicular Magnetic Recording (PMR) was invented in 1975 by Shunichi Iwasaki, a Professor of Tohoku University at that time, and his research group. The first paper to report successful experimental demonstration of high density recording by PMR was published in 1977 in the IEEE Transactions of Magnetics. After 28 years of intensive works, perpendicular magnetic recording was commercialized on hard disk drive (HDD) in 2005. It achieved great success used for all hard disk drives within a couple of years. In this paper, an innovation of PMR research and its engineering HDD integration processes from the invention to the commercialized products are reviewed.