Let $M$ be a (real) manifold. Recall that an _analytic structure_ on $M$ is an atlas such that all transition maps are real-analytic (and maximal with respect to this property). (There's also a sheafy definition.) So in particular being analytic is a structure, not a property. Is it true that any topological manifold can be equipped with an analytic structure? Can any $C^\infty$ manifold (replace "analytic" by "$C^\infty$" in the previous paragraph) be equipped with an analytic structure (consistent with the smooth structure)?