A photomontage is the combination of 2 or more photographs joined together to make one single image. This can be done either digitally or manually using scissors. Photomontage is often used as a means of expressing political dissent. It was first used as a technique by the Dadaists in 1915 in their protests against the First World War.
John Stezaker 
My Edits
For this edit I used to portrait images that had the model facing the same way. I put both images into photoshop then used the ‘rectangular marquee tool’ on the black and white one to select the eyes and make a new layer via copy. Then I placed that layer on top of my colour image and lined the features up. 
I made this edit by printing out tow portrait pictures of two different people and using scissors and glue. I cut out the faces for both images then experimented with them by putting them next to each other.