Breeders are trying all sorts of things to produce ever smaller pigs, from breeding runt to runt, to severely limiting their food, to breeding for the dwarfism gene. All of these practices result in health problems for the pig. An underfed, stunted pig's organs will outgrow their tiny, misshapen bodies, resulting in eventual organ failure. Runts often have life-long health issues if they make it past the critical infant stage. Dwarfism comes with a whole host of health issues, just as in humans.
There are supposedly all kinds of new breeds out there. Teacups, micro minis, royal dandies, Juliana, pixie pigs, pocket pigs, chipmunk pigs, nano pigs, these are all made-up marketing ploys to part unsuspecting consumers from their money.