These are examples of the oldest, the newest, and the future tube stock on the London Underground. The first picture is the 1972 stock that now runs on the Bakerloo Line. The second picture is the S7 stock which is currently the newest stock (along with the S8) that was first introduced to service in 2010 and runs on the Circle, District, Hammersmith and City Lines. And the third picture is a mock up of how the new Piccadilly Line trains will look when they are (hopefully) introduced in 2025.