"Cells at Work!" is an anime series that anthropomorphizes the various cells and microorganisms within the human body, presenting them as characters in a bustling, workplace-like environment. The narrative centers on the daily lives and functions of these cells, personified as workers maintaining the body's health. The protagonist, AE3803, is a cheerful and somewhat clumsy red blood cell responsible for delivering oxygen and nutrients throughout the body. Her counterpart, U-1146, is a stoic and highly skilled white blood cell (neutrophil) tasked with combating pathogens and infections.

The series unfolds as a series of episodic adventures, with each episode depicting a specific biological process or health scenario. AE3803 often finds herself in precarious situations, such as getting lost or encountering dangerous bacteria, while U-1146 frequently intervenes to protect her and eliminate threats. Other key characters include Platelets, depicted as adorable children responsible for clotting and wound repair, and Killer T Cells, aggressive enforcers that destroy infected or abnormal cells. Macrophages, elegant but deadly immune cells, also play a significant role in maintaining order and eliminating invaders.

The narrative explores various health-related events, such as injuries, allergies, and infections, with each scenario dramatized as a crisis or mission for the cells. For example, a common cold is portrayed as a viral invasion, while a scrape or cut becomes a chaotic construction site requiring the coordination of platelets and other cells. The series also delves into more severe conditions, such as cancer, depicted as rogue cells that evade the immune system's defenses.

Throughout the series, the interactions between the cells highlight their roles and the importance of their teamwork in maintaining the body's health. The tone balances lighthearted humor with moments of tension, particularly during battles against pathogens. By personifying biological processes, "Cells at Work!" provides an engaging and educational perspective on human anatomy and physiology, making complex concepts accessible to a broad audience.