(written from a Production point of view)
Hawaiian prop and creature designer Wah Ming Chang (2 August 1917 – 22 December 2003; age 86), surreptitiously contracted by Desilu Productions Inc., was responsible for the design and construction of many familiar items used in Star Trek: The Original Series.
Chang's association with Star Trek began in 1964 when he was hired to create makeup and props for "The Cage" by Producer Robert Justman. His first contribution was the prosthetic Talosian head make-up. He then designed the laser pistol for the pilot after Justman was unsatisfied with the original designs. He was later hired to design various items for the regular series, including the famous tricorder, flip-top communicator props, and the Romulan Bird-of-Prey studio model. He was usually sent a copy of the script for the episode he was hired to work on, and he began to work on design, make sketches, and models in his home taking his cue from the scripts. Chang's association with Star Trek ended in middle of the second season after the fabrication of dozens of tribble props, conceivably due to the budget cuts resulting from Desilu's purchase by Gulf+Western.
Originally his work was not credited, nor did Chang take the credit afterwards and his work for Star Trek went unnoticed well into the 1970s. It was through fandom and its corresponding Star Trek convention circuit of the 1970s that his contributions became known. The reason for this state of affairs was eventually revealed when Producers Herb Solow and Justman published their book Inside Star Trek: The Real Story in 1996. In it (pp. 119-120) Justman described that it all originated from a conflict with the propmaker's union. Chang as a non-member was neither allowed per their rules to fabricate props for the show, nor was he allowed to join, creating a catch-22 situation. At Justman's urging, who considered Chang's work superior to anything elsewhere available by far, the studio devised a ruse to make it appear that the props were bought as pre-existing and off-the-shelf from Chang, which was allowed under union rules, and it was reflected as such in Desilu's purchase orders sent to Chang. As a result Chang could neither be officially credited for his contributions, nor be mentioned in the, otherwise thorough, contemporary reference book The Making of Star Trek, where most of his hand-held props were prominently featured. The ruse however, was uncovered by the union just prior to the start of the second season, as mentioned by Justman in his book, and might have served as the additional reason why Chang's talents were not called upon again from the mid-second season onward, as the union was now alerted to Chang's involvement. 
Career outside Star Trek
Already a recognized sculptor, Chang became crippled at age 31 by the effects from polio, but it did not prevent him and his company Project Unlimited, Inc. to carve out a career in the motion picture industry by designing puppets, costumes, sets, make-up, and special effects for a number of films, most notably producer/director George Pal's science fiction and fantasy features, including Tom Thumb (1958), The Time Machine (1960, with Whit Bissell and for which he designed the iconic title object and the Morlocks), and The Wonderful World of the Brothers Grimm (1962, with Ian Wolfe and Jon Lormer). He also worked on classic pictures such as The King and I (1956), Spartacus (1960, with Jean Simmons, Peter Brocco, John Hoyt, Arthur Batanides, William Blackburn, Paul Lambert, Dick Crockett, Seamon Glass, and narration by Vic Perrin), and Mutiny of the Bounty (1962, with Antoinette Bower, Torin Thatcher, and stunts by Paul Baxley). Chang designed the famous headdresses worn by Elizabeth Taylor in Cleopatra (1963, with John Hoyt).
On television, Chang designed masks, creatures, and special effects for The Outer Limits (1963-1965), where his cooperation with Star Trek associate producer Robert Justman began. He was also a dinosaur model maker on the television series Land of the Lost (1974-1976) and also worked on the special effects of the original Planet of the Apes (1968, with Lou Wagner, James Daly, Paul Lambert, Billy Curtis, Jane Ross, and Felix Silla, and music by Jerry Goldsmith).
In 1994, he was given the George Pal Memorial Award by the Academy of Science Fiction, Fantasy & Horror Films for his contributions to the genres.
The extent of Chang's Star Trek contributions is preserved for posterity, as Desilu's purchase orders were later donated to UCLA and stored in their archives.  Several of them were reproduced in the aforementioned Inside Star Trek reference book, as well as in the 1997 book Star Trek: The Original Series Sketchbook (indicated below by their price quotations).
Designed and manufactured props
- The flip-top communicator; designed and constructed for US$1,019.20
- The tricorder; designed and constructed for US$572.00
- The Talosian head make-up for "The Cage"
- The Humanoid bird for "The Cage"
- The laser pistol in "The Cage" and "Where No Man Has Gone Before"
- The Fesarius, Balok's cube, and Balok's puppet in "The Corbomite Maneuver"
- The M-113 creature in "The Man Trap"
- The Vulcan lute in "Charlie X", et al.
- The Romulan Bird-of-Prey in "Balance of Terror"
- The Romulan helmets and ears in "Balance of Terror"; designed and constructed for US$748.80
- The anthropoid creature in "The Galileo Seven"
- The Gorn costume in "Arena"
- The flying parasite in "Operation -- Annihilate!"
- The tribbles in "The Trouble with Tribbles"
- Life and Sculpture of Wah Ming Chang, Wah Ming Chang, 1989 (ISBN 0962529311)
- Wah Ming Chang: Artist and Master of Special Effects, Enslow Publishers, 1995 (ISBN 0894906399)