Petitgrain smells green, woody, citrusy, and floral with a slightly bitter edge. It's often used in perfumes and colognes. 
Source
Petitgrain is extracted from the leaves and twigs of the bitter orange tree, citrus aurantium. The name "petitgrain" translates to "little grains". 
Uses
Petitgrain is often used as a top or middle note in blends. It's also used in perfumes and colognes with notes of bergamot, lemon, and orange. 
Related varieties
There are a couple of varieties of petitgrain, including "citronnier" and "mandarin petitgrain". "Citronnier" is distilled from the leaves of the lemon tree, and "mandarin petitgrain" has a thyme-like scent.
This comes in a 240ml bottle