In Conways game of life, there is a the concept of an orhpan pattern.
Basically, an orphan is a finite pattern such that each configuration containing that pattern is a Garden of Eden (a pattern that cannot have a predecessor).
The smallest such pattern has not been found yet. A computer search 2011, restricted to symmetric orphans gave a pattern that fits in a 10x11 rectangle.
Thus, the smallest orphan will fit in a 10x11 rectangle, but it is probably smaller. Note that there are roughly $2^{10 \times 11}$ possible configurations that fit within these bounds.
