  We prove some "universality" results for topological dynamical systems. In
particular, we show that for any continuous self-map $T$ of a perfect Polish
space, one can find a dense, $T$-invariant set homeomorphic to the Baire space
${\mathbb N}^{\mathbb N}$; that there exists a bounded linear operator $U:
\ell_1 \rightarrow \ell_1$ such that any linear operator $T$ from a separable
Banach space into itself with $\Vert T\Vert\leq 1$ is a linear factor of $U$;
and that given any $\sigma$-compact family ${\mathcal F}$ of continuous
self-maps of a compact metric space, there is a continuous self-map
$U_{\mathcal F}$ of ${\mathbb N}^{\mathbb N}$ such that each $T\in {\mathcal
F}$ is a factor of $U_{\mathcal F}$.
