One Cell


This is pretty dull. Click Start and you'll see our lone cell dies because it has fewer than two live neighbours.

Two Cells


This is also pretty dull. Click Start and you'll see both cells dies because each has fewer than two live neighbours.

Three Cells - The Blinker


This is... interesting? Click Start and you'll that the pattern oscillates.

On the first generation:

This is inverted on the second generation and again on the third and so on..

The Life world has its own rich lexicon. An oscillator is a pattern that repeats itself after a fixed number of generations (this is the period). This particular oscillator is called a Blinker and has a period of 2.