What are the 16 optical illusions you have to look twice at to understand?

There are numerous optical illusions that challenge our perception, but some notable examples include the Müller-Lyer illusion, where lines of equal length appear different due to arrow-like ends; the Necker cube, which can be perceived from two different perspectives; and the dress that appeared to be both blue and black to some and white and gold to others. Other examples include the Penrose triangle, which creates an impossible shape, and the Kanizsa triangle, where outlines suggest a triangle that isn't actually there. These illusions reveal the complexities of visual perception and how our brains interpret images.