What happens when you hold Alt and click on the animation stopwatch?

When you hold Alt and click on the animation stopwatch in Adobe After Effects, it creates an expression for the property you are animating. Expressions are powerful tools within After Effects that allow you to use code to control animations and relationships between different properties. This feature is particularly useful for creating dynamic animations, as you can modify parameters using simple scripts, enabling more complex behaviors without needing to keyframe every change manually.

For instance, if you wanted an object's position to be influenced by another object's position, you could write an expression that links the two properties, allowing for real-time updates and adjustments. This is a fundamental element of motion graphics workflows, as it saves time and can lead to more flexible animation techniques. By creating an expression, you open up many possibilities for automating and enhancing your projects.