Imagine a towering skyscraper, its impressive height built not equally on every floor, but resting predominantly on a few crucial, foundational levels. This, surprisingly, mirrors the architecture of today’s leading large language models (LLMs), like those powering ChatGPT. New research reveals that a select few early layers, dubbed "cornerstone layers," play a disproportionately large role in a model's overall performance. This study, focusing on the inner workings of LLMs, uses a clever method borrowed from game theory—Shapley values—to measure each layer's individual contribution. Think of it like figuring out each player's importance in a team sport, but instead of players, we're looking at the building blocks of an AI model. The findings are striking: removing a single cornerstone layer can cause catastrophic performance failure, reducing the model to little more than a random word generator. These critical layers seem to handle the most fundamental aspects of language processing, forming the bedrock for all subsequent computations. Other layers, while still contributing, are far less critical; removing them results in only minor performance dips. This suggests a degree of redundancy, opening exciting possibilities for streamlining LLMs, making them leaner and more efficient. So, what do these cornerstone layers actually *do*? One theory is that they wrestle with the raw input, turning human language into the numerical representations that the AI can understand. The remaining layers, it seems, add details and nuance, but the groundwork—the cornerstone—is essential. This discovery is more than just an academic curiosity. It has profound implications for how we build and understand future AI. By focusing on these essential layers, researchers may unlock ways to enhance model performance, reduce computational bloat, and perhaps even address long-standing issues like AI bias and hallucinations. The quest to build truly intelligent machines may well hinge on understanding these crucial few layers—the cornerstones of artificial intelligence.