I have a small pillbox that belonged to my grandmother. I have used it to hold tiny keepsakes for more than forty years. Similar items were sold in Italian tourist shops and were very popular in the 1940s to late 1950s. They are mosaic but are more often than not misidentified as micro mosaic.
Below is what micro mosaic looks like. In short, micromosaic items are made from much much smaller tessserae (about 1,400 tiles of glass per square inch) than mosaic, and look almost like paintings.
If you are interested in reading more about the difference between mosaic and micromosaic, this article is very interesting.