# The Render Tree, Layout, and Paint You've got a DOM tree and a CSSOM tree from Phase 1. Neither one, alone, is enough to draw anything - the DOM doesn't know what's visible or where, and the CSSOM doesn't know what elements exist. The browser combines them into something new, then does two more passes before a single pixel changes color. ## Building the render tree **What it actually is.** The render tree is DOM nodes merged with their computed CSS, but with one important filter: only nodes that will actually be visible on the page make it in. **What it does in real life.** ``, `