After Particleman a second Spore prototype has now been released at the official Spore page. BIOME in the words of Maxis is:

…a programmable cellular automata simulator that allows users to develop simple “SimCity-like” grid simulations

The way SimCity works in its core is based on Conway’s Game of Life which he developed in 1970. In the game, neighbouring cells influence (or eat) one another, leading to an ever changing pattern of “cells” on the grid. This ofcourse can be readily compared to e.g. a NIMBY or YIMBY “cell” influencing nearby residential zones in SimCity. Maxis’ explanations goes on to say:

BIOME uses a language based on chemical stoichiometry, the notation system used to describe chemical reactions. Cells in a BIOME simulation change state the same way that chemicals change when exposed to other chemicals

Systems such as this can be used to simulate phenomena such as forest fires, disease epidemics, animal migration patterns and crystallization

BIOME supports both rectangular and spiral cellular automata configurations. The spiral configuration was used to study stochastic, self-propagating star formation (the process whereby the ignition of a star promotes the creation of more stars) on the galactic scale.

If that doesn’t make sense to you, keep in mind the disclaimer on the Spore prototype page:

Keep in mind these (prototypes) are not tested, supported or even easily explained.