The tiny dots on the surface of the skin are the openings of the hair follicles. Each of them contains a sebaceous gland which is responsible for the production of skin`s oils. These glands are bigger on the forehead and the nose, so the pores are more visible on these parts. The size of the pores depends on the genes, and typically fair-skinned individuals have pores on the small side. On the other hand, those with darker skin have larger pores. The skin type is yet another important factor! Dry skin is less prone to pores compared to oily skin.
There are other factors that affect pore size. For instance, dead skin cells and trapped sebum from a pimple which stretches out pores. Collagen loss which comes with aging is yet another thing that increases the visibility of pores. UV rays are known to weaken the collagen, so they also make pores look much bigger. Ultimately, squeezing a pimple is likely to permanently widen the pores.