What is the organism that contracts faster than any human muscle and baffles science?

A team of researchers from United States universities has described the contraction mechanism of the single-celled organism Spirostomum ambiguum. The organism is capable of reducing itself to one-quarter of its length in less than five milliseconds.

This rapid movement is achieved through a network of proteins activated by ions, a process that contracts faster than any human muscle and has baffled science.