Storing and manipulating images in 4d matrix / Cell Array

I am relatively new to matlab and need to do image processing.

I have a series of images, each a trial under different experimental conditions that I wish to subtract from one another.

I would like to create a 4d matrix, containing each 2d grayscale image with its corresponding trial number or experimental and time/frame number.

I have tried using cell arrays, but it seems incredibly difficult to do data manipulating using these.

What is the best way to go about this?

[KALYAN ACHARJYA]

Inputs are 2D gray image, you can save two/multiple 2D images in a 3D, why are you considering 4D here?