Brane phenomenology

String theory is probably the best candidate for a fundamental quantum theory of all interactions, including the Einstein gravity. The theory contains only one free parameter, the string scale MS. It was conjectured that in type 1 strings the string can be lowered all the way down to the TeV range. Similar ideas for lowering the fundamental Planck scale in theories with submillimeter gravitational dimensions appeared, as an alternative solution to the gauge hierarchy problem, and simultaneous, as a new way for lowering the grand unified theory scale in theories with large (TeV) dimensions. In this paper the goal of the author is to review some of the ideas which emerged from this new picture: millimeter and TeV extra dimensions, gauge coupling unification, neutrino masses and localized gravity. (author)