The Planet Neptune, being so distant from The Sun, takes a long time to complete its year. As a consequence, once Neptune enters a Zodiac sign, it is there for a long time.
During this orbit Neptune, the modern ruling planet of Pisces, first entered Pisces from Aquarius in 2011, but the retrograde motion soon took it back across the cusp back in to Aquarius. A confusing effect for all Pisceans and Aquarians attuned to the effects of Neptune.
Neptune re-entered Pisces in February 2012, and will remain here until 2025, a period of domination punctuated by aspects from all of the other faster moving astrological bodies. When the effects of other planets on Pisces are easing, the influence of Neptune will return to the fore.
In many ways the fact Pisces is already ruled by Neptune adds to their generally dreamy and cerebral nature. Pisces do make ideal adviser at those times we need some spiritual guidance. Add Neptune and many Pisces will feel themselves completely conjoined with the divine. Many other people looking at Pisces from the outside may well interpret this as this as being mysterious at best and at times nothing more than a fantastical illusion.
The good news for Neptune in Pisces is the sense of wonderment this will afford their dreams and desires. Expect Pisces to be the bringer of the future to the rest of us over the next decade. Any major advances in theoretical sciences, conceptual arts or new genres of writing or cinema could be driven by the dreams of Pisces.