How to make preview pictures bigger on my iphone?

Like when yo open up the iphone photos app, and you can see all the photos in your album? Can I change the size of the preview like I can with the text size?

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1.Place your thumb and pointer finger at opposing points of the screen as if preparing to pinch a cheek.
2.Gently move your fingers away from each other. Note that the speed at which your fingers are spread will influence the rate of zoom.
3.To zoom back out, reverse the motion and gently "pinch" your fingers towards each other while keeping contact with the screen.