Wood travels through war-torn Afghanistan, crossing the Oxus River into Central Asia and the Silk Road city of Samarkand where, in a drunken brawl, Alexander killed the friend who had previously saved his life.

This episodes the nature of the cosmos on the micro and atomic scales, using the Ship of the Imagination to explore these realms. Tyson describes some of the micro-organism that live within a dew drop, demonstrating parameciums and tardigrades. He proceeds to discuss how plants use photosynthesis via their chloroplasts to convert sunlight into chemical reactions that convert carbon dioxide and water into oxygen and energy-rich sugars. Tyson then discusses the nature of molecules and atoms and how they relate to the evolution of species. He uses the example set forth by Charles Darwin postulating the existence of the long-tongued Morgan's sphinx moth based on the nature of the comet orchid with pollen far within the flower. He further demonstrates that scents from flowers are used to trigger olfactory centers in the brain, stimulating the mind to threats as to aid in the survival of the species. Tyson narrates how Greek philosophers Thales and Democritus postulated that all matter was made up of combinations of atoms in a large number of configurations, and describes how carbon forms the basic building block for life on earth due to its unique chemical nature. Tyson explains on the basic atomic structure of protons, neutrons, and electrons, and the nature of nuclear fusion that occurs in most stars. He then discusses the existence of neutrinos that are created by these nuclear processes in stars, and that detecting such sub-atomic particles which normally pass through matter require subterranean facilities like the Super-Kamiokande that were used to detect neutrinos from the supernova SN 1987A in the Large Magellanic Cloud before light from the explosion were observed due to their ability to pass through matter of the dying sun. Tyson compares how neutrinos were postulated by Wolfgang Pauli to account for the conservation of energy from nuclear reactions in the same manner as Darwin's postulate on the long-tongued moth. Tyson concludes by noting that there are neutrinos from the Big Bang still existing in the universe but due to the nature of light, there is a "wall of infinity" that cannot be observed beyond.

This episode is centered around how science, in particular the work of Clair Patterson (voiced in animated sequences by Richard Gere[33]) in the middle of the 20th century, has been able to determine the age of the Earth. Tyson first describes how the Earth was formed from the coalescence of matter some millions of years after the formation of the Sun, and while scientists can examine the formations in rock stratum to date some geological events, these can only trace back millions of years. Instead, scientists have used the debris from meteor impacts, such as the Meteor Crater in Arizona, knowing that the material from such meteors coming from the asteroid belt would have been made at the same time as the Earth. Patterson also examined the levels of lead in the common environment and in deeper parts of the oceans and Antarctic ice, showing that lead had only been brought to the surface in recent times. He would discover that the higher levels of lead were from the use of tetraethyllead in leaded gasoline resulting in government-mandated restrictions on the use of lead.

The constellation of the Pleiades provides a vehicle for us to explore a series of paradoxes and epochal discoveries for humanity. The untold story of the modern "sisters of the sun," the early 20th century female astronomers, led by two deaf women, at Harvard who catalogued the stars. It's also the story of the young British woman who joined forces with them, her defiance of the world's leading expert, and how she taught the world what the stars are really made of.

This episode explores the palaeogeography of Earth over millions of years, and its impact on the development of life on the planet. Tyson starts by explaining that the lignin-rich trees evolved in the Carboniferous era about 300 million ago, then explains on the nature of plate tectonics that would shape the landmasses of the world and the asteroid impact that initiated the Cretaceous–Paleogene extinction event, leaving small mammals as the dominate species on earth. Earth's landmasses are expected to change in the future and postulates what may be the next great extinction event.

Among the ranks of the Wehrmacht there was limited opposition to Hitler. Most officers initially felt enthusiastic about the prospect of war and were grateful to Hitler whose war-mongering had furthered their personal careers. Furthermore all soldiers had to make an oath of allegiance to the Führer and, up until the very end, there were many who felt unable to break this pledge. There were, however, some officers who opposed Hitler. For some it was on moral grounds and for others because they thought that his military tactics would lose them the war. There were plots against Hitler and attempted coups, the best known being the July bomb plot led by Claus von Stauffenberg. Some soldiers refused to bear arms and were shot, others deserted, others still carried out quiet acts of sabotage and subversion. By and large, however, the Wehrmacht carried out the orders Hitler issued, even if it involved perpetrating acts of atrocity.