This study revisits and updates the estimates of the number of human and bacterial cells in the human body. The authors integrate the most recent data to provide revised estimates for the total number of bacteria in a 70 kg "reference man" as 3.8 × 10^13, and for human cells as 3.0 × 10^13. They identify the hematopoietic lineage as the dominant contributor to the total human cell count, accounting for approximately 90% of the total. The analysis also updates the widely cited 10:1 ratio of bacteria to human cells, showing that the number of bacteria is actually of the same order as the number of human cells, with a total mass of about 0.2 kg. The study revisits the assumptions and methodologies used in previous estimates, providing detailed calculations and uncertainty ranges. It also examines the variation in the B/H ratio across different population segments, including gender, age, and obesity. The findings highlight the importance of accurate and up-to-date estimates in understanding the human body's cellular composition and the role of the microbiome.This study revisits and updates the estimates of the number of human and bacterial cells in the human body. The authors integrate the most recent data to provide revised estimates for the total number of bacteria in a 70 kg "reference man" as 3.8 × 10^13, and for human cells as 3.0 × 10^13. They identify the hematopoietic lineage as the dominant contributor to the total human cell count, accounting for approximately 90% of the total. The analysis also updates the widely cited 10:1 ratio of bacteria to human cells, showing that the number of bacteria is actually of the same order as the number of human cells, with a total mass of about 0.2 kg. The study revisits the assumptions and methodologies used in previous estimates, providing detailed calculations and uncertainty ranges. It also examines the variation in the B/H ratio across different population segments, including gender, age, and obesity. The findings highlight the importance of accurate and up-to-date estimates in understanding the human body's cellular composition and the role of the microbiome.