During my freshman year of college, I met a Chinese ESL student whom I befriended. During my first visit to her dorm, she offered me a bowl (actually, it was a Glad plastic storage container) of some sort of sweet, grey soup (or something to that effect). It had the consistency of sludgy water, but I thought it tasted good. I forgot to ask her what it was called, and it wasn't until recently that I found something similar in an Asian grocery store. After mixing up a cup, I realized that it was the exact same thing. And that if you don't add cold water before adding hot water, it congeals and looks likes sludgy water. I like to make the soup thicker, anyway, so it has a consistency more along the lines of thin mud. Yum.
The soup is Vietnamese, but it's also popular in China for supposedly keeping grey hair at bay (something to do with the fact that it's good for the blood and liver). It's also good for the kidneys, so the packaging claims. I have the instant version, but it can also be made by soaking rice in water for an hour, then grinding it in a blender with toasted black sesame seeds and later boiling it with some water and sugar.