Classics - Released in 2006, featured reinterpreted versions of Classics characters with modern updated designs using the Transformers Cybertron aesthetic. Universe - Released in 2008, generally stuck much closer to updated designs than full on reinterpretations (Prowl, Sunstreaker / Sideswipe, Silverbolt), also went with a wider scope paying tribute to other lines (Beast Wars, Armada, even Animated got referenced by the line). Generations - Released in 2010, generally focuses on more obscure characters who've not had toys since either the original release in the 80s or never got one at all back in the day. Also featured toys based on the War for Cybertron video game. Reveal the Shield - Coming in 2011, will feature more Classics styled characters which straddle the line between update and reimagination. Generally seems to feature characters who are more mainstream, and a couple of Movie series recolours as well. Ooo 'eck!
