The ocean is home to some of Earth's most important producers. Single-celled organisms in the ocean are responsible for more than half of Earth's productivity, as well as most of its oxygen. Phytoplankton are single-celled, plantlike organisms. That is, they have chloroplasts and perform photosynthesis, but are not true plants, which are typically multicellular. By introducing the students to the phytoplankton, teachers familiarize them with some of the planet's most abundant producers. The students will have a tentacle up on most Americans, many of whom are ocean illiterate and don't realize that the ocean keeps the Earth warm enough to support life, supplies oxygen, and does much more. This sequence of lessons gives students the opportunity to conduct field and laboratory work, construct their own equipment, and design their own experiment--skills that every student should develop in middle school. (Contains 6 figures.)