An evaporating colloidal particle–laden droplet leaves behind a ring-like residue after drying. We routinely observe this ubiquitous phenomenon for dried coffee drops; thus, it is known as the "coffee ...

This was originally identified by X user Tibor Blaho, who spotted a mention of “image-gen-watermark-for-free” in a beta version of ChatGPT for Android. Android Authority then followed this up with a ...