  We provide sufficient conditions for a regular graph $G$ of growing degree
$d$, guaranteeing a phase transition in its random subgraph $G_p$ similar to
that of $G(n,p)$ when $p\cdot d\approx 1$. These conditions capture several
well-studied graphs, such as (percolation on) the complete graph $K_n$, the
binary hypercube $Q^d$, $d$-regular expanders, and random $d$-regular graphs.
In particular, this serves as a unified proof for these (and other) cases.
  Suppose that $G$ is a $d$-regular graph on $n$ vertices, with $d=\omega(1)$.
Let $\epsilon>0$ be a small constant, and let $p=\frac{1+\epsilon}{d}$. Let
$y(\epsilon)$ be the survival probability of a Galton-Watson tree with
offspring distribution Po$(1+\epsilon)$. We show that if $G$ satisfies a (very)
mild edge expansion requirement, and if one has fairly good control on the
expansion of small sets in $G$, then typically the percolated random subgraph
$G_p$ contains a unique giant component of asymptotic order $y(\epsilon)n$, and
all the other components in $G_p$ are of order $O(\log n/\epsilon^2)$.
  We also show that this result is tight, in the sense that if one asks for a
slightly weaker control on the expansion of small sets in $G$, then there are
$d$-regular graphs $G$ on $n$ vertices, where typically the second largest
component is of order $\Omega(d\log (n/d))=\omega(\log n)$.
