This passage about the discovery of the Spemann organizer from Developmental Biology, 6th Ed by Scott F. Gilbert (2000) not only nails it, but nails it with inspirational style*:
But this research has found levels of complexity far deeper than Spemann would have conceived, and just as Spemann’s experiments told us how much we didn’t know, so today, we are faced with a whole new set of problems generated by our solutions to older ones.
Surveying the field in 1927, Spemann remarked:
We still stand in the presence of riddles, but not without hope of solving them. And riddles with the hope of solution – what more can a scientist desire?”
The challenge still remains.
*…and, admittedly, tortured sentence structure.
UPDATE: Hat tip to my human genetics research partner, Dr. Jennifer Taylor.