Short answers, pulled from the story.
Michael J. Cullen opened the first supermarket named King Kullen on the 4th of August 1930 in a former garage in Jamaica, Queens, New York City. This establishment was defined by self-service, separate product departments, discount pricing, and volume selling.
The transition to supermarkets caused a brutal economic shift for the Great Atlantic and Pacific Tea Company known as A&P which destroyed thousands of retail jobs. By 1938 A&P had opened over 1,100 supermarkets and closed 5,950 grocery stores to reduce money-losing operations from 44 percent to 18 percent.
The first fully stocked supermarket outside the United States appeared in Rome, Italy in 1956 as part of an American Way exhibit presented by the U.S. Department of Agriculture. This modest staging included about 2,500 items and was much larger than anything the world had ever seen at that time.
Modern supermarkets use circulation to control traffic flow and place high-draw products in separate areas to draw consumers through the store. They place high impulse and high margin products in predominant areas to grab attention and use power products on both sides of the aisle to create increased product awareness.
The number of American supermarkets tripled from 1,200 in 32 states in 1936 to over 3,000 in 47 states in 1937. The total count reached well over 15,000 by 1950 as the format exploded across the country.
The British online supermarket Ocado was the first successful online-only supermarket and it uses a high degree of automation in its warehouses. This technology allows Ocado to expand into providing services to other supermarket firms such as Waitrose and Morrisons.