Source: http://gizmodo.com/5549904/coming-soon-printable-prescription-pills
Only a small portion of the pill you swallowed earlier is actually an active ingredient, the rest is filler. That bit of information is what caused researchers to explore a way to start printing active ingredients onto blank filler tablets.
Aside from allowing medication dosages to be customized during the printing process, this method would also allow active ingredients to be affective more rapidly as they'd be on the outside of tablets rather than encased inside a pill.
Unfortunately the process could only be applied to about one percent of the pills on the market at this time, but researchers remain hopeful about figuring out a way to implement it more widely. [Discovery via Geekologie]
Picture by Dean812