Mosaics are an art form that has been around for thousands of years. What we recognize as a mosaic today, pieces of glass or ceramics set into patterns in concrete or grout, had its beginnings in ancient Greece. Before that, people made things that were similar to modern mosaics, but were different in a couple of vital ways.
Most experts agree that the origins of mosaics started in the Orient. One example of this is in Chaldean society around 2000 BC. Instead of glass, the Chaldeans used small cones of painted clay that were set into surface of columns for decorations. Fused glass was first discovered by the Egyptians and they began decorating everything with it, including their ships. From Egypt, the use of fused glass spread slowly across the world. Early on, in Greece, mosaics were crafted out of pebbles that had been worn down in water. The pebbles (or ciottoli) were set in the pictures carefully so that shading and designs were created to make the pictures more realistic. They also used thin strips of lead to highlight and define lines in the pictures. Often these mosaics were used for floor decorations, so your entire floor could be one huge mosaic. Not only was your home more beautiful and interesting, it was functional as well.
By the 4th century BC, the art of mosaics changed greatly. The Romans expanded on and made changes to the art that had been passed on to them by the Greeks. The Romans began to use smaller pieces of both stone and glass. Because they were using smaller pieces, the pictures could be more detailed and complex. Mosaics could be found everywhere from floors to ceilings to even walkways where mosaics were made from stones and pieces of marble.
In due time, the Romans passed their mosaic making skills onto the Byzantines who took it to even greater heights. The number of mosaics and the skill and intricacy involved in them are phenomenal during this period in Byzantium. With the fall of Byzantium in the 15th century, however, mosaic making fell out of favor and was not practiced much if at all until the 19th century. Since then mosaics have persisted in one form or another.
Today, mosaics are alive and well. It is an easy art to learn, but it can take a lifetime of infinite possibilities to master. The variations and potential for so many different pieces is infinite. You can buy items for your mosaics, including pre-cut tiles or glass. You can use broken dishes from around your house, or even random items you find such as shells or rocks. Inspiration is all around you, from historical examples to more modern mosaic art. Many examples of ancient mosaics still exist, some of them remarkably intact and well kept. You could attempt to recreate a drawing or painting that you like into a mosaic, or you could take a historical example and try to recreate it. The possibilities are endless and the scope of your project could be huge or small, depending on what you plan on using it for.