Fading images

**I wanna to do something that:
I have one image, second one is on it and it’s cutted for small parts. How to make it fading? You know, when I hover mouse on it, it disapper slowely and the first image appear. Each part I wanne to make this way. I tried to make it with Transform effect but when I take the cursor from the part it appear again. Could You help me?

Thx in advance