A surgical instrument is a tool or device for performing specific actions or carrying out desired effects during a surgery or operation, such as modifying biological tissue, or to provide access for viewing it. Over time, many different kinds of surgical instruments and tools have been invented. Some surgical instruments are designed for general use in all sorts of surgeries, while others are designed for only certain specialties or specific procedures. Classification of surgical instruments helps surgeons to understand the functions and purposes of the instruments. With the goal of optimizing surgical results and performing more difficult operations, more instruments continue to be invented in the modern era. History Many different kinds of surgical instruments and tools have been invented and some have been repurposed as medical knowledge and surgical practices have developed. As surgery practice diversified, some tools are advanced for higher accuracy and stability while some are invented with the completion of medical and scientific knowledge. Two waves in history contributed significantly to the development of surgical tools. In the 1900s, inventions of aseptic surgeries (maintenance of sterile conditions through good hygiene procedures) on the basis of existing antiseptic surgeries (sterilization of tools before, during, and after surgery) led to the manifestations of sale and use of instrument sterilizers, sterile gauze, and cotton. Most importantly, instruments were advanced to be readily and effectively sterilized by replacing wooden and ivory handles with metals. For safety and comfort concerns, the tools are made with as few pieces as possible. Hand surgery emerged as a specialty during World War II, and the tools used by early hand surgeons remain in common use today, and many are identified by the names of those who created them. Individual tools have diverse history development. Below is a brief history of the inventors and tools created for five commonly used surgical tools. Scissors Mayo scissors, created by one of the mayo brothers, was one of the inventions of the Mayo clinic (established by Dr.William Worrall Mayo and his two sons, Dr. William James Mayo and Dr. Charles Horace Mayo in the 1880s). Mayo scissors have semi-blunt ends and they are either straight or curve-bladed. The straight blades are used for cutting tissue near wounds, and curves are used for cutting thick tissue. Metzenbaum scissors were invented by Myron Metzenbaum (1876-1944). This tool was widely used for tonsillectomy (the surgical removal of the tonsils). The lighter