Topics covered in this episode: the structure of the atom (proton, neutron, electron, and the quarks that go into the former two); the forces that hold the atom together (strong and electromagnetic); the shells around the atomic nucleus, and the orbitals making up those shells (with spiffy 3D depictions of the orbitals); nuclear fusion (with a summary of the Sun's internal reactions) and fission (with a description of radiocarbon dating).
The second half of the episode is, traditionally for Assignment Discovery docs, dedicated to a selected single subject, and this time it's the fascinating topic of black holes. They lead up to it with the history of research of gravity (Newton, Einstein) and light (Newton, Michell, Einstein), culminating in an excellent review of the modern theories on black holes, and the associated speculations.
Great visual and verbal presentation. They put sound effects like clicks and whooshes into all the space-based scenes, though, which can be very annoying, and clashes with the otherwise fantastic content. 8/10.