An After Effects project can be incredibly complex, filled with dozens of individual layers organized into pre-compositions, and those compositions nested within other compositions. Each layer may contain several different effects, keyframes, and expressions. So, what happens when your client sees the render and asks that one specific clip in the video be replaced? How can you make a substituion and keep all applied effects, keyframes, and the clip length intact? It's actually very simple. Here's how you can do it: