How Dutch painters studying in Italy came to be influenced by Caravaggio, and took his style back to Utrecht, where they became known as Utrecht Caravaggists.
ter Brugghen
Take some blue glass, grind it, and turn it into paint: Smalt is one of the strangest of pigments. It extensively used until replaced by Prussian Blue in the early 1700s, and is making a comeback.
The Eclectic Light Company 