The kidney is one of the most important organs, which maintains our body system. Kidney filters the blood of impurities, accomplishes homeostatic functions, excretes waste products, and secretes hormones which stimulate red blood cell formation or control blood pressure. According to the recent statistics from the Korean Society of Nephrology, one out of seven adults in Korea has kidney disease. However, only 3% recognized that they have kidney disease, since the symptoms of the kidney disease do not appear until it is too late. Editorial board selected the "chronic kidney disease" as the focus of this supplement issue to arouse the interest of the kidney disease research and its importance. It is our wish that all our readers of this issue will receive in-depth knowledge about the kidney research in Korea and the effort of many researchers.

Lastly, I would like to appreciate Professor Suhnghwon Kim, Yong-Soo Kim, Kyu Hun Choi, Young Ok Kim, Tae-Hyun Yoo, and the all other contributors who submitted their valuable manuscripts.

Thank you.