Mathematicians recognize the Dutch mathematician L.E.J. Brouwer (1881–1966) as the first to construct a rigorous proof of the invariance of dimension. In fact, Brouwer published two proofs of dimensional invariance, the first in 1911 and the second in 1913, both full of deep insights. Moreover, in the course of developing these proofs he made highly significant contributions to the whole domain of topology. He injected an entire array of new methods into the field and raised its standard of rigor to a high level.