The Hubble Sequence of Galaxies helps us organize them by appearance. When you don't know anything, first put them in buckets of "this one is like that one", and hope correlations appear. Here, they do! This is part of my complete intro Astronomy class that I taught at Willam Paterson University and CUNY Hunter. • Galaxy Types: Elliptical, spiral, and irregular. • Elliptical Galaxy Characteristics: Elliptical shape, no internal structure, composed of old stars, and lack gas and dust. • Elliptical Galaxy Size: Range from dwarf ellipticals with a few million stars to giant ellipticals with trillions of stars. • Distance of Celestial Objects: Stars are tens to thousands of light years away, while galaxies are millions to hundreds of millions of light years away. • Lenticular Galaxy Characteristics: Lens-shaped with a disc-like structure, a central bulge, but no spiral arms or interstellar gas, often appearing reddish due to older stars. • Galaxy Types: Hubble’s tuning fork diagram categorizes galaxies based on appearance, including elliptical, lenticular, and spiral galaxies (Sa, Sb, Sc, Sd), but doesn’t necessarily reflect their evolutionary paths. • Star Formation Indicators: Pink glows in galaxies, such as M81 and the Whirlpool Galaxy, signify star formation regions, particularly Orion nebulas and ionized hydrogen. • Spiral Arm Dynamics: Gas passing through spiral arms triggers star formation, resulting in pink clouds of young stars on one side and older, brighter stars on the other as they rotate through the density wave. • Spiral Arm Formation: Spiral arms are regions of star formation, with gas and dust on elliptical orbits that create density waves. • Universe Scale: The images showcase the vastness of the universe with numerous distant galaxies. • Spiral Galaxy Characteristics: Spiral galaxies, like NGC 891, are identified by their edge-on view, dust and gas presence, and star formation regions. • Barred Spiral Galaxies: These galaxies feature a central bar-like structure and are sites of active star formation. • Magellanic Clouds’ Features: Irregular shape, active star formation, and close proximity to the Milky Way. • M82 Galaxy Characteristics: Irregular galaxy with a dark dust cloud and pink glow of ionized hydrogen gas, potentially a former spiral galaxy. • Dwarf Irregular Galaxies: Small, distorted galaxies with millions to tens of millions of stars, often exhibiting active star formation. • Dark Matter in Dwarf Galaxies: Dwarf galaxies’ low mass necessitates dark matter for gravitational stability. • Galaxy Mass Ranges: Spiral galaxies range from a billion to over a trillion solar masses, elliptical galaxies from 100,000 to ten trillion solar masses, and irregular galaxies fall in between. • Galaxy Structure: Spiral galaxies have a disc, a spheroidal component, rapid rotation, and gas and dust; elliptical galaxies are only spheroidal, contain only old stars, and have mostly random rotation. Overall, the segment emphasizes clear definitions, underlying geometry, and practical observing guidance so viewers can connect the concept to the real sky.