"What is Life?" is a scientific exploration that delves into the intersection of physics and biology. The book presents the idea that life, at its most basic level, operates according to the laws of physics and chemistry. It introduces the concept of an "aperiodic crystal" that contains genetic information in its configuration of covalent chemical bonds, which later inspired the discovery of the structure of DNA. The book also discusses entropy and negentropy, suggesting that life feeds on negentropy to counteract the natural process of increasing entropy.

This seminal work in the field of genetics presents the results of a series of experiments conducted on pea plants, which led to the discovery of fundamental laws of inheritance. The author meticulously cross-bred different varieties of peas and meticulously recorded the traits of their offspring, leading to the formulation of the principles of segregation and independent assortment. These principles, which underpin modern genetics, explain how traits are passed from parents to offspring and how different traits are inherited independently of each other.