tool chapter 19 : the beast that wants to know chapter 20 : the anthill brain chapter 21 : infinite bandwidth chapter 22 : talking microbes part three and tell chapter 23 : the neuron rosetta stone chapter 24 : desperate housewives chapter 25 : the house neuron , the senate neuron , and the intelligent designers chapter 26 : the doomsday machine and the houdini electron chapter 27 : a brief history of time chapter 28 : let there be light !