We are more than happy to see the completion of this special issue in honor of Dr. Jong Shin Yoo’s retirement. Since the establishment of the Korea Society for Mass Spectrometry (KSMS)—the publisher of Mass Spectrometry Letters, he has been one of the core members and served as the second president of KSMS from 2006 to 2007. Dr. Yoo received in Ph.D. degree in Chemistry for Mass Spectrometry from the Michigan State University in 1992, and worked for the Harvard School of Public Health, Boston, USA, as a post-doctoral fellow. Since coming back to Korea in 1993, he has been working on biological mass spectrometry at the Korea Basic Science Institute. He currently holds a joint professorship in Graduate School of Analytical Science and Technology at Chungnam National University. In addition to actively serving as the second president of KSMS, he also served as a president of Korea Human Proteome Organization (KHUPO) in 2008 as well as an international HUPO council member. Dr. Yoo’s research interests have long involved in biological mass spectrometry such as (1) developing bioinformatics tools for N- and O-glycoproteomics, (2) mass spectrometry (MS)-based biomarker development for early diagnosis of cancer, (3) proteogenomic studies for Chromosome-based Human Proteome Project in HUPO, and (4) the instrumental development of 15T-FTICR mass spectrometers. Thirty years of devotions to MS-related research have brought him more than 200 peer-reviewed articles in the leading scientific journals such as Mass Spectrometry Reviews, Scientific Reports, Molecular & Cellular Proteomics, Analytical Chemistry, and Journal of Proteome Research. This special issue contains five excellent articles to honor him. The contributions are from some of the scientists with whom Dr. Yoo has long been collaborating. The topics of the five articles include chromosome-based proteome, N-glycosylation analysis of recombinant proteins, biomarker discovery from serum of scrub typhus patients, MS analysis of low molecular weight collagen, and glycosylation monitoring of antibody therapeutics. We would like to express our sincere gratitude to Dr. Yoo for his effort and devotion for KSMS and look forward to our continued collaborations in the next stage.