Code review has significantly evolved from its inception in the 1970s, initially introduced as "Fagan Inspections" by IBM engineer Michael Fagan, who emphasized error detection without room for design discussions. Through the decades, the practice transformed from cumbersome in-person evaluations to self-reviews known as desk checks in the 1990s, albeit adopted by only a minority of developers. The shift to digital in the early 2000s, driven by advancements in source control systems like Git, enabled global collaboration and led to the creation of Google's Mondrian, a pioneering web-based code review tool by Guido van Rossum. Mondrian's user-centric design, inspired by Gmail, focused on actionable code reviews. This evolution continued with the rise of GitHub, which adapted the code review process to prioritize open-source maintenance, showcasing repository-wide interactions and utilizing Pull Requests to foster collaborative discussions. Today, code review is an integral part of software engineering, with distinct systems catering to both open-source and closed-source environments, reflecting its journey from a niche practice to a cornerstone of code quality assurance.