Wild thyme and sav'ry
Set around their cell

sweet to the taste
And fragrant to the smell
Set rows of rosemary
With flow'ring stem,
And let the purple vi'lets
Drink the stream.

Virgil, "Georgica", 20 B.C

The bees gather pollen for their nourishment from,different plants and carry it as "pollen load" into the hive.
Pollen is the main protein source for the honeybees and presents for them a perfect food.
By collecting pollen bees pollinate the flowers, 40000 plant species are pollinated world wide by the bees.
The importance of bee pollination for ecology and agriculture is immense.
The economic importance for the USA is about 18.9 billions of dollars
In the USA in other countries beekeepers are paid by the peasants for pollination services.
The importance of bees for the pollination and multiplication of wild plants is also immense, but cannot be quantified in a money value. References to bee bee pollen in ancient Egyptian papyri dating back to 5000 BC, describe it "a life-giving dust."

  Every pollen has a story: a video presentation by Jonathan Drori

In human diet pollen is an exquisite functional food and many health enhancing effects,
are attributed to it. It is an excellent source of antioxidant polyphenols.
It has a clinically proven effect against prostatitis
(non-malignant enlargement of the prostata gland).

You can download for free the Pollen Book,if you are member of the Bee Hexagon Knowledge Network (free membership offered).
The book will be updated, look at the publication date.