Carnegie molecular biologist Joseph Gall discusses the work of groundbreaking microscopists, biologists, zoologists, and geneticists with Bill Nye, "The Science Guy," as The Science Channel counts down the greatest science discoveries of our time. In a series of segments filmed at the Embryology Department of the Carnegie Institution, Dr. Gall discusses

• Antony van Leeuwenhoek, the 17th-18th century microscopist, who first described bacteria, sperm, and living protozoa;
• Robert Brown, the 19th century botanist, who coined the term "nucleus"  and discovered "Brownian Motion," the constant jiggling exhibited by minute objects seen under a microscope;
• Theodor Schwann, the 19th century zoologist, who developed the cell theory (in collaboration with Matthias Schleiden, a botanist);
• Walther Flemming, the 19th century biologist, who gave the first accurate description of nuclear division and named it "mitosis";
• Eduoard Van Beneden, the 19th biologist, who provided the first accurate description of the behavior of chromosomes during fertilization;
• August Weismann, the 19th century biologist, who predicted the requirement for meiosis (the "reduction division" of the chromosomes) and who formulated a theory of development based on the behavior of chromosomes; and
• Thomas Hunt Morgan, the early 20th century geneticist, who introduced the fruit fly Drosophila for genetic analysis and who provided the first genetic map.

More information, including air times, is available at The Science Channel.