The Poincaré group, named after Henri Poincaré (1906), was first defined by Hermann Minkowski (1908) as the group of Minkowski spacetime isometries. It is a ten-dimensional non-abelian Lie group, which is of importance as a model in our understanding the most basic fundamentals of physics. For example, in one way of rigorously defining exactly what a subatomic particle is, Sheldon Lee Glashow has expressed that "Particles are at a very minimum described by irreducible representations of the Poincaré group."