I go to sea to study the smallest organisms that live there — the beneficial bacteria that make up the base of the ocean's food web and provide 50 percent of the oxygen we breathe. If you took a teaspoon of seawater from the coast of Florida and counted all the bacteria in it, you would find about 5 million cells (and you would be counting for a long time). We know so little about these tiny wonders, but one of them may hold the key to a new antibiotic, cancer drug, or detoxifying agent. The only way to find out is to learn more about them.