  I review recent results in three topics of the M-world: (i) Scales. (ii) New
dark matter candidates. (iii) Cosmological solutions from p-branes. The three
topics are discussed in the framework of Ho\v{r}ava-Witten compactifications.
Part (iii) includes comments on cosmological solutions in M-theory describing
nucleation of universes through instanton effects and expansions toward
asymptotically flat or anti-de-Sitter spaces.
