1 Its cost, on average, is $650, compared to $400 for take-home trays and under $100 for over-the-counter bleaching trays or whitening strips. 2  Results can be unpredictable, depending on factors such as age, heredity and the type of staining that is present.
Plankton (singular plankter) are a diverse group of organisms that live in the water column of large bodies of water and that cannot swim against a current. They provide a crucial source of food to many large aquatic organisms, such as fish and whales.
Usually, plankton are small, like these tiny copepods, but some plankton are large, like this jellyfish. There are two basic kinds of plankton, phytoplankton and zooplankton. Phytoplankton means plant plankton and includes all kinds of drifting plants, like microscopic diatoms and algae.