Memory window

The memory window was a device invented by the Celestial Toymaker. Both Steven and Dodo looked into it when they arrived in the Celestial Toyroom. Steven saw images from his adventures on Kembel in 4000 and Paris in 1572 and Dodo saw herself in school uniform the day her mother died. The First Doctor told them the window was hypnotic, and that the Toymaker would have used it to dominate their minds. (TV: The Celestial Toymaker)