Front-end developers sit atop a massive amount of technology, often treating whole pieces of our application as opaque functionality. Grab a hard hat and follow me down into the internals of Preact, a tiny 3kb alternative to React. Along the way we’ll shed light on fundamentals like JSX & Virtual DOM, demystify DOM diffing, and see how keys work up-close. On our way back to the surface, we’ll stop at the Museum of Lost Hours to see some performance and size optimizations. Hope you’re not afraid of the dark!