The Brief: This meme format uses an image of a grain of rice next to the world's smallest computer to depict something that is even "smaller" than either of those two things.
Grain of rice/world’s smallest computer memes features a photo of a micro-computer created by researchers at the University of Michigan. This computer, which is currently the smallest in the world, fits on a single grain of rice.
A meme format using this image is particularly popular on the Dank Memes subreddit. These memes usually compare the two objects to something that is even tinier. Usually, that object is not actually very small, but the meme hyperbolically says that it is to make a point. Often, these memes make fun of people such as anti-vaxxers or flat earthers for having “tiny” brains due to their beliefs.
A GIF version of this meme: