Real talk about post production — a lot, A LOT, of thorough planning and organization goes into even the simplest of animations. One way to make an animators’ life more enjoyable and organized (in After Effects) is by pre-composing layers. As an editor/motion graphics editor, I can proudly say that I use pre-comps in every single AE project I work on. Pre-composing is immensely useful for managing and organizing complex compositions. Essentially, you gain more power over those layers — and who doesn’t like that?

In After Effects pre-composing is: “the process of packaging a series of layers into a new composition”. It’s essentially the same as grouping layers in Illustrator or Photoshop. Here’s the keyboard shortcut in AE to pre-compose: Command+Shift+C.
Here are some things you can do by pre-composing:
Pre-composing a single layer is useful for adding animation, effects, transform properties, or masks to that layer and that will then be applied to all of the layers within — resulting in cleaner animation that’s a bit simpler to obtain.
Pre-composing multiple layers places them in a new composition which replaces the layers in the original composition — resulting in a more aesthetically pleasing composition that’s a little easier to manage.
Apply complex changes to an entire composition — You can create a composition that contains multiple layers, nest the composition within the overall composition, and animate and apply effects to the nested composition so that all the layers change in the same ways over the same time period.
Here’s an example of how pre-comps are essential. This is a “simple ‘ol” 17-second-long animation that I created for the EPA WARN project we produced in 2018.
Now let’s dig in —This pedigree chart is a quick and easy representation of how in just these 17 seconds, multiple pre-comps (and pre-comps nested inside pre-comps) complete this animation.

The second pedigree chart is a slightly-more-interesting visual repetition of the complexities of this animation.

That’s just a small glimpse into the mind of a motion graphics editor. One take away from all this post-production mumbo-jumbo: Command+Shift+C (Mac) is your friend.