For quite some time, I had been complaining about lack of origami books about curved crease techniques. But now we have one! Curved Origami by Ekaterina Lukasheva has a bunch of curved crease projects from very simple to moderately complex. This is one of the first models in the book.
For those who don’t know, a “curved crease” is a crease that makes a curved line on the paper. A curved crease will not fold all the way, meaning that the folded models necessarily make a 3-dimensional shape. The typical folding method involves drawing and scoring curved lines on paper (possibly with the assistance of templates, compasses, french curves).
I really admire how simple these water drops are. (Yeah, I know rain drops aren’t actually shaped like that.)