John Kimball is a fictional character from the television series Breaking Bad. He is known for his role as a high school chemistry teacher who turns to cooking and selling methamphetamine after being diagnosed with terminal cancer. His character explores themes of morality, family, and the consequences of choices. Throughout the series, Kimball's transformation from a mild-mannered educator to a drug kingpin highlights the complexities of human nature. His relationships with other characters, including Jesse Pinkman and Walter White, further develop the narrative, showcasing the impact of his decisions on those around him.