Updated project metadata. This project aimed at missing protein identification from human placental tissue, combining sample preparation and mass spectrometry technology development.For sample preparation, low molecular proteins were enriched by C18 solid phase extraction, SDS-PAGE and MWCO filter. For LC-MS/MS analysis, micro-HPLC fractionation was carried out coupled with LUMOS instrument. Proteome Discoverer 2.2 software was used for data analysis to identify missing proteins.