Millefiori -- an Italian term meaning "a thousand flowers" -- is the name of the age-old technique. 

Millefiori is a type of Murano glass that has been incorporated with various layers of colors to create beautiful flower-like patterns. Millefiori, which literally means a thousand flowers, is the denomination of a type of cylindrical, long glass rod which contains a specific pattern along its entire length, so that when cut into slices from one end, the particular pattern will be revealed. It is completely handmade of authentic Murano glass . This style of glass has been around since the Middle Ages and more recently, has been produced for fine jewelry.