Large and infinite extra dimensions

The emphasis in the developmet of theories with more than three spatial has recently shifted towards ``brane world'' picture, which assumes ordinary matter (with possible exceptions of gravitons and other,, particles which interact very weakly with matter) is trapped to a-dimensional submanifold --- brane --- embedded in fundamental-dimensional space. In the brane world scenario, extra dimensions may be, and even infinite; they may have effects, directly observable in current fothcoming experiments. On the basis of simple field-theoretic models, ideas in this direction are exposed at a non-expert level.