Seed beads
Seed beads are uniformly shaped, spheroidal beads ranging in size from under a millimeter to several millimeters. The most poplular seed bead size is 11/0 ("eleven-aught"), but sizes range from 22/0 (the smallest, I believe) to 6/0 or 5/0 (the largest). Seed beads were most commonly used for
loom and
off-loom bead weaving in the past, but during the last decade Japanese cylinder beads have become increasingly popular. These exist in two versions: Delicas® made by Miyuki and Antiques made by Toho. Unlike regular rounded seed beads, the cylinder beads are quite uniform in shape and size and have large holes for their size. Because the ends are flat instead of rounded, work created with cylinder beads has a flat instead of a bumpy texture.
Most of today's good quality seed beeds are made in Japan or the Czech Republic. Japanese seed beads are more uniform than the Czech ones and have larger holes for the same size of bead.
Here is a description of bead making from a visit to the Miyuki bead factory in Japan