A team of scientists spent 2.5 years traveling the oceans, over 70,000 miles, and came back with a startling discovery. There was once thought to be 30,000 species of plankton but they discovered more than 2 million species. The diversity, and strangeness, is astounding. One species combines together to form a chain 40 meters long while another forms symbiotic colonies, living within each other.
Watch the BBC story: