A small, perforated, basket-like container with a hinged opening. Loose tea is placed inside the infuser, which is then closed and lowered into a teapot, whereupon boiling water is added. The tiny holes in the infuser allow the water to interact with the tea leaves. A tiny chain with a hook at one end is attached to the top of the infuser -- the hook slips over the rim of the teapot so the infuser can easily be retrieved, thereby straining the tea leaves. There are also single-cup infusers, which are shaped like two perforated teaspoons that fasten together. Tea infusers are usually made of stainless or chromed steel, although there are also porcelain and silver models.