The Italian designer and architect Pier Giacomo Castiglioni is the second of the three Castiglioni brothers. Like his brothers, Pier Giacomo Castiglioni studied architecture at Milan Polytechnic, taking his degree in 1937. In 1938 Pier Giacomo Castiglioni and his elder brother, Livio, founded a practice in Milan, which the youngest brother, Achille, joined in 1944. All three Castiglioni brothers were interested in both technology and art. Livio left the joint practice in 1952 to go his own way.
Pier Giacomo Castiglioni is regarded as the intellectual equal of his brother Achille. Until his untimely death in 1968, Pier Giacomo collaborated with Achille on numerous designer objects. In 1957 the exhibition "Colori e forme nella casa d'oggi" (Colors and Forms in Today's Home) was mounted at the Villa Olmo in Como, where Achille and Pier Giacomo Castiglioni annoyed specialists with their vision of a modern lifestyle because what they showed was a colorful jumble of styles that incorporated old and new furnishings instead of uniformly styled interiors. Achille and Pier Giacomo Castiglioni showed many of their designs, including for the first time their "readymades". "Mezzadro", a stool consisting of a tractor seat mounted on a substructure and "Sella", a telephone stool with a bicycle saddle as a seat were not made until many years later, by Zanotta.
The two brothers were particularly successful with the lighting they designed for Arredoluce, Flos, and Artemide. They playfully explored new possibilities for form, linking technical innovation and Minimalist economy of means to produce highly functional objects which were just as aesthetically satisfying as they were practical. In 1955 the Castiglionis designed "Luminator" for Arredoluce; their "Taraxacum" hanging lamp dates from 1960 and the hanging lamp "Splügen Bräu" for Flos was launched in 1961. Another Castiglioni design for Flos was the 1962 die lamp "Arco", which links the qualities of floor and hanging lamps.
The Castiglioni brothers not only exerted a strong influence on the younger generation of Italian designers. Pier Giacomo Castiglioni taught design at Milan Polytechnic from 1946 until his death. Achille Castiglioni also taught interior decoration and industrial design there from 1982 until 1986 and was a professor of industrial design at Turin Polytechnic from 1970 until 1980.
The Museum of Modern Art collection owns many works by Achille and Pier Giacomo Castiglioni.