The Alexander Sarcophagus, c. 312 B.C.E., Pentelic marble and polychromy, found in Sidon, 195 x 318 x 167 cm (İstanbul Archaeological Museums). Speakers: Dr. Elizabeth Macaulay-Lewis and Dr. Steven Zucker. Created by Steven Zucker and Beth Harris.

The Bier of Iskandar (Alexander the Great), folio from the Great Mongol Shahnama (Il-Khanid dynasty, Tabriz, Iran), c. 1330, ink, opaque watercolor and gold on paper, 57.6 x 39.7 cm (Freer Gallery of Art, Smithsonian Institution, purchase — Charles Lang Freer Endowment, F1938.3) This video focuses on one particular painting within one particular 14th century manuscript now commonly called the Great Mongol Shahnama. This is only one of many versions of the Shanama, the great epic of Iran. Speakers: Dr. Massumeh Farhad, Chief Curator and The Ebrahimi Family Curator of Persian, Arab, and Turkish Art, Freer Gallery of Art and Arthur M. Sackler Gallery, Smithsonian Institution and Dr. Steven Zucker.

This site teaches Arithmetic with Polynomials and Rational Expressions to High Schoolers through a series of 4333 questions and interactive activities aligned to 26 Common Core mathematics skills.

This site teaches High Schoolers how to create equations through a series of 298 questions and interactive activities aligned to 5 Common Core mathematics skills.

This site teaches Reasoning with Equations and Inequalities to High Schoolers through a series of 5909 questions and interactive activities aligned to 36 Common Core mathematics skills.

This site teaches Structure in Algebraic Expressions to High Schoolers through a series of 3482 questions and interactive activities aligned to 26 Common Core mathematics skills.

How can we improve the speed of a (deterministic) primality test? Created by Brit Cruise.

The properties of organic molecules depend on the structure, and knowing the names of organic compounds allow us to communicate with other chemists. We'll be learning about different aspects of molecular structure, including common functional groups and conformations.

Chiricahua Apache artist Allan Houser’s “Earth Song” is the signature sculpture on display at the Heard Museum in Phoenix, AZ. Created in 1979 from Alabama marble, it depicts an Apache man singing a song of respect, a prayer to Mother Earth. Houser is considered the Grandfather of Contemporary Native American Sculpture for creating works that are grounded in a respect for all indigenous cultures. Discover more reasons why “Earth Song” is a masterpiece with David Roche, Dickey Family Director and CEO of the Heard Museum. Video by Bank of America. Created by Smarthistory.

Allele frequencies in populations and how they differ from genotype frequencies. Created by Sal Khan.

A gene as a stretch of DNA on a chromosome. Alleles as versions (sequence variants) of a gene.

Outline of the 1973 Allende Coup in Chile and Pinochet's Junta (this video under CC-BY-SA). Created by Sal Khan.

There are a number of European alliances that contributed to the broad scope of World War I. Prominent among these are the 1839 Treaty of London, which promised that the United Kingdom would protect Belgium's neutrality, the 1879 Dual Alliance treaty between Germany and Austria-Hungary to protect each other in the event of Russian attack, the 1892 Franco-Russian Military Convention that promised mutual assistance in the face of attack, the Triple Entente linking the United Kingdom and France (and later Italy), and the Triple Alliance linking Germany, Austria-Hungary, and Italy (at first). Created by Sal Khan.

Washington Allston, Elijah in the Desert, 1818, oil on canvas, 125.09 x 184.78 cm / 49 1/4 x 72 3/4 inches (Museum of Fine Arts, Boston). Created by Beth Harris and Steven Zucker.

Sir Lawrence Alma-Tadema, A Reading from Homer, 1885, oil on canvas, 36-1/8 x 72-1/4 inches / 91.8 x 183.5 cm (Philadelphia Museum of Art). Created by Beth Harris and Steven Zucker.

Infrared cameras now reveal concealed drawings under the surface of many of the Renaissance's most revered paintings. Learn how this radical drawing technique was done.

In this art history video discussion Beth Harris and Steven Zucker examine Albrecht Altdorfer's "The Battle of Issus," 1529, oil on panel. Alte Pinokothek, Munich.