This study presents a comprehensive molecular cell atlas of the human lung using single-cell RNA sequencing (scRNAseq). The researchers analyzed ~75,000 human cells from various lung tissue compartments and circulating blood, identifying 58 distinct cell populations, including 41 of the 45 previously known cell types and 14 new ones. The atlas provides detailed gene expression profiles and anatomical locations of these cell types, revealing their biochemical functions, transcription factors, and optimal markers. It also identifies cell targets of circulating hormones, predicts local signaling interactions, and maps the expression changes of immune cells following egression from circulation. The study further explores the evolutionary conservation of lung cell types and their transcriptomes, finding significant diversification in human lung cell types compared to mice. This comprehensive resource offers insights into lung physiology, medicine, and the molecular basis of diseases and evolutionary changes.This study presents a comprehensive molecular cell atlas of the human lung using single-cell RNA sequencing (scRNAseq). The researchers analyzed ~75,000 human cells from various lung tissue compartments and circulating blood, identifying 58 distinct cell populations, including 41 of the 45 previously known cell types and 14 new ones. The atlas provides detailed gene expression profiles and anatomical locations of these cell types, revealing their biochemical functions, transcription factors, and optimal markers. It also identifies cell targets of circulating hormones, predicts local signaling interactions, and maps the expression changes of immune cells following egression from circulation. The study further explores the evolutionary conservation of lung cell types and their transcriptomes, finding significant diversification in human lung cell types compared to mice. This comprehensive resource offers insights into lung physiology, medicine, and the molecular basis of diseases and evolutionary changes.