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Organisms and their parts somehow ‘know’ when to stop growing. As computers count in an algorithmic, logarithmic or binary way, so does biology ‘count’ in its own biochemical way. Self-assembly is a process that spontaneously creates order. At the molecular scale, self-assembling components don’t ‘know’ where to go – but they get there. Particles combine and settle in so many ways, randomly fitting together, that eventually, bit by bit, they become complex and can build even further. Preparing a sample for atomic force microscopy, complex self-assembled molecules settle onto a mica surface, where they will soon be imaged. (Also see “Wings.”) Self-assembly is a ubiquitous process at the molecular scale (crystals, viruses, cytoskeletons) and macroscopic scale (dust bunnies, sand dunes, stars). Tree forms are also ubiquitous in nature and culture, and are self-organizing at many scales (rivers,carbohydrates, traffic patterns). These universal forms can be seen seemingly everywhere. Entire organisms – be they trees, whales, frogs, or humans – develop from a single cell. When cells divide, each half innately ‘knows’ which part of the organism it should become next. The Sierpinski gasket is a mathematical fractal constructed by repeatedly cutting the middle out of each triangle. Or, more akin to crystal growth, it may be generated by starting with a layer of 0′s with a single 1, then building new layers by placing a 0 above and between each pair of identical bits, while placing a 1 above and between each pair of differing bits. Nature builds powerful computers, your brain being a prime example. Molecular self-assembly allows scientists to create electrical circuits by growing them.
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