(From original article by Rachel Kaufman, via National Geographic News)
December 3, 2009–The world’s smallest known orchid (pictured)—just over 2 millimeters (0.08 inch) across and nearly see-through—has been discovered nestled in the roots of another flower in Ecuador…
Lou Jost, an ecologist with the EcoMinga plant-conservation foundation, has studied the plants of the South American country’s mountainous forests for 15 years.
Earlier [in 2009] he’d collected an orchid of a larger species to study in his greenhouse. “Several months later I saw this tiny plant,” he said.
Find the rest of this article at National Geographic.
Another article, from The Independent.
...free your imagination... 
Good picture, good news for orchid lovers, but You should say “among the smallest orchids in the world”, not “smallest orchid in the world”.
Just a bit bigger than 2mm ? There are smaller orchids, in Madagascar for instance, where you can find (hardly and scarcely, you have to search and be lucky) orchids with flowers **under** 1mm in their biggest dimension and the complete plant between 1 and 2 cm (small Angraecums with many white/translucent flowers in a “big” < 1cm inflorescence.
thanks for the comment!
if you know of an orchid that was discovered before the article was published that actually measured smaller, please supply the scientific name- or if like this one, it’s unnamed, some form of reference to the discovery, and i’ll most happily amend the article! 🙂