Jimmy Miller presents an unconventional approach to understanding large codebases: building visualizers rather than attempting to comprehend millions of lines at once. His method focuses on turbopack, Next.js's Rust bundler, demonstrating how targeted exploration beats comprehensive analysis when learning unfamiliar code.

The technique involves setting specific goals, making random edits, fixing discovered issues, reading to answer questions, and creating visual representations. Miller documents his process using a real bug report involving tree shaking in Next.js, showing how to identify the minimal case that reproduces the issue.

This approach transforms code learning from overwhelming to manageable by focusing on concrete problems rather than abstract understanding. The author's practical methodology includes side quests like packing and unpacking Next.js versions for testing, demonstrating that effective code exploration requires persistence alongside structured techniques.