Video in Video Effect

Hello everyone !

This is my first post and I'm from Poland so sorry for my English.

I've got a question. Is anyone know how make a video transition like this from one video to another:





I mean when camera is "enter" to next video (in TV scrren or laptop) ?

I know that you need a green field and track it, then replaced video, but what is the simplest solution in AE ?

Maybe are any tutorials of this effect ?

Thanks & greets !