Beginning in the early 1900s, modern chemistry sets targeted younger people with the intention to popularize chemistry. In the United States, Porter Chemical Company and the A. C. Gilbert Company produced the best known sets. Although Porter and Gilbert were the largest American producers of chemistry sets, other manufacturers such as the Skilcraft corporation were also active.
John J. Porter and his brother Harold Mitchell Porter began The Porter Chemical Company in 1914. Their initial purpose was to sell packaged chemicals, but they soon introduced kits. John researched the experiments, while Harold wrote the instruction manuals. Their earliest toys, under the "Chemcraft" trademark, were "chemical magic" sets, selling for less than one dollar (or about $25 in 2017). By the 1920s, they sold six different sets, the largest of which sold for $25 (or about $320 in 2017). Their range of toys broadened throughout the 1930s. In the 1950s it was possible to buy toys featuring radioactive ores, such as the "Gilbert U-238 Atomic Energy Laboratory," which included a Geiger counter and cloud chamber.
Alfred Carlton Gilbert earned money by performing magic tricks while a medical student at Yale. He and John Petrie formed the Mysto Manufacturing Company (later the A. C. Gilbert Company) in 1909, and began selling boxed magic sets. By 1917, they sold chemistry sets, which they produced through World War II, in spite of restrictions on materials. Robert Treat Johnson, noting the number of chemistry students at Yale whose interest in the science began with a chemistry set, argued the production of chemistry sets was a "patriotic duty."
Toy companies promoted chemistry sets through advertising campaigns, the "Chemcraft Chemist Club" and its accompanying "Chemcraft Science Magazine", comic books, and essay contests such as Porters "Why I want to be a scientist". The goal of attracting students to a potential career in chemistry was often explicit in the sets naming and promotion. Chemistry sets may have been the first American toys marketed toward parents with the goal of "improving" children for success in later life.
The target market for chemistry sets was almost exclusively boys, deemed "young men of science." However, during the 1950s, Gilbert introduced a set targeting girls. They sold the set in an attractive pink box, but the set identified girls as "laboratory assistants" or "lab technicians," not scientists.  
In 1971, a Johnny Horizon Environmental Test Kit was licensed by the U. S. Department of the Interior and produced by Parker Brothers. It included four air pollution tests and six water pollution tests for young environmental scientists.
The Johnny Horizon Environmental Test Kit was marketed to both boys and girls.
Well-known chemistry sets from the United Kingdom include the 1960s and 1970s sets by Thomas Salter Science (produced in Scotland) and later Salter Science, then the "MERIT" sets through the 1970s and 1980s. Dekkertoys created a range of sets which were similar, complete with glass test tubes of dry chemicals.