Pore size is genetically determined, so you can't actually shrink pores. The bad news is that pore size is genetically determined, so you can't actually shrink pores. However, some products and treatments can minimize the appearance of pores, but none of them are permanent solutions.
As we age and our skin loses its elasticity, it will often stretch or sag. This can cause pores to expand over time, making them more visible as we age. During hormonal periods, the overproduction of oil can make pores appear larger, when excess sebum collects on the skin's surface, magnifying these small openings.