# Connes' Embedding Problem and Lance's WEP

Abstract: We will show that a II_1-factor embeds into the
ultraproduct of the hyperfinite II_1-factor if and only if
it satisfies the von Neumann algebraic analogue of Lance's
weak expectation property. This result implies that free
group factors (and all other embeddable factors) are built
up from the inside (not just in distribution) by the
hyperfinite II_1-factor in a way which naturally mixes
W* and operator space notions.