In this After Effects Tutorial VideoFort Jon teaches you the basics of Expressions by starting out with the Wiggle expression. An expression in After Effects can be used in lieu of keyframing to animate layers. Start out by loading your footage into the comp. Then drop down the transform controls and select Position. Then go up to effects and select add expression. In the comp timeline, next to position, transform.position should appear. Delete this and type in wiggle(5, 10). This will make the layer move 5 times in one second, by a factor of five pixels. From here you can alter either value as you please. If you want to specify a start point for your expression you need to add a Slider Control from the Effects. From there you will need to delete the 10 value and with the cursor in place of the 10, select the Expression Pick Whip and select the slider control. You will notice another expression has been added in place of the 10. Now you can use the Slider Control to keyframe the expression. Expressions can be used anywhere you can keyframe. Show us what you can create by posting your projects in the comments!