Moving image to back- and foreground over time

[BlackHawkDown]

Hello,

I'm using Adobe After Effects. I have a composition with several layers. One layer consists of an image which is shown for around 20s. At time point 10s I would like to bring the image to the foreground (relative to the other layers) and at time point 15s I would like to move it again to the background.

How can I achieve this?

Thank you very much!

[dj.summitt]

You'll want to use 3D layers in After Effects. You will basically keyframe the z position at different times. 
Here's a basics on 3D layers. https://helpx.adobe.com/after-effects/using/3d-layers.html