"Cells at Work: Baby!" is a spin-off of the popular "Cells at Work!" series, focusing on the biological processes within a newborn baby's body. The manga explores the challenges faced by the cells as they adapt to the unique environment of an infant, which differs significantly from that of an adult. The narrative centers on the interactions and efforts of various anthropomorphized cells, each representing a specific type of cell in the human body, as they work to maintain the baby's health and development.

The protagonist is a red blood cell, tasked with delivering oxygen and nutrients throughout the body. Alongside this red blood cell, other key characters include a white blood cell, responsible for combating pathogens, and a platelet, involved in clotting and wound healing. These cells must navigate the complexities of a newborn's immune system, which is still developing and more vulnerable to infections and illnesses. The story highlights the increased workload and heightened vigilance required from the cells to protect the baby from external threats.

Throughout the series, the cells encounter various medical conditions and scenarios specific to infants, such as neonatal jaundice, respiratory distress, and common infections. The manga provides detailed explanations of these conditions, emphasizing the biological mechanisms at play and the collaborative efforts of the cells to address them. The narrative also touches on the importance of breastfeeding, vaccination, and other factors crucial to a baby's health.

The interactions between the cells are characterized by teamwork and dedication, reflecting the intricate and cooperative nature of the human body's biological systems. The manga maintains an educational tone, blending scientific information with a compelling storyline to engage readers while providing insights into neonatal physiology. By focusing on the unique challenges of a newborn's body, "Cells at Work: Baby!" offers a fresh perspective on the cellular world, expanding on the original series' premise with a specific emphasis on infancy.