Rubin vase

Rubin's vase (sometimes known as the Rubin face or the figure–ground vase) is a famous set of ambiguous or bi-stable (i.e., reversing) two-dimensional forms developed around 1915 by the Danish psychologist Edgar Rubin. They were first introduced at large in Rubin's two-volume work, the Danish-language Synsoplevede Figurer ("Visual Figures"), which was very well received; Rubin included a number of examples, such as a Maltese cross figure in black and white, but the one that became the most famous was his vase example, perhaps because the Maltese cross could also be easily interpreted as a black and white beachball.

https://en.wikipedia.org/wiki/Rubin_vase