This is Klein's bottle, an only object that can exist on four dimensions. In four dimensions the neck of the bottle penetrates to its body without even touching it.
In the field of mathematics, Klein bottle refers to a non-directional plane, such as a two-dimensional plane, there is no distinction between "inside" and "outside".
In topology, the Klein bottle is a non-orientable topological space. It was first proposed by the famous mathematician Felix Klein, but Klein’s original intention was, "Kleinsche Fläche", which is the Klein plane, which has no internal and external distinctions, but later it became Klein Rhein bottle.
Unlike the cup we usually use to drink water, this object has no "edge" and its surface will not end. It is different from a spherical surface. A fly can fly directly from the inside of the bottle to the outside without passing through the surface, that is, it has no distinction between inside and outside. Because of this, the Klein bottle is never filled with water.
Source: daydaynews.com
