+ Origami

The goal of this art is to create a representation of an object using geometric folds and crease patterns preferably without gluing or cutting the paper, and using only one piece of paper.
Almost every origami book begins with a description of the basic origami techniques which are enough to construct those models described as basic or intermediate in difficulty. These include fairly standard diagrammatic representations of the basic folds like valley and mountain folds, pleats, reverse folds, squash folds, and sinks. There are also standard named bases which are used in a wide variety of models, for instance the bird base is an intermediate stage in the construction of the flapping bird.
It is common to fold using a flat surface but some folders like doing it in the air with no tools especially when displaying the folding. Many folders believe no tool should be used when folding. However a couple of tools can help especially with the more complex models. For instance a bone folder allows sharp creases to be made in the paper easily, paper clips can act as extra pairs of fingers, and tweezers can be used to make small folds. When making complex models from origami crease patterns, it can help to use a ruler and ballpoint embosser to score the creases. Completed models can be sprayed so they keep their shape better, and of course a spray is needed when wet folding.
The practice and study of origami encapsulates several subjects of mathematical interest. For instance, the problem of flat-foldability (whether a crease pattern can be folded into a 2-dimensional model) has been a topic of considerable mathematical study.
The problem of rigid origami ("if we replaced the paper with sheet metal and had hinges in place of the crease lines, could we still fold the model?") has great practical importance. For example, the Miura map fold is a rigid fold that has been used to deploy large solar panel arrays for space satellites.
There may soon be an origami airplane launched from space. A prototype passed a durability test in a wind tunnel on March 2008, and Japan's space agency adopted it for feasibility studies. (Spring Into Action, designed by Jeff Beynon, made from a single rectangular piece of paper)