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 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.