Original: Davros experimented on living Kaled cells to find the ultimate mutated form of the Kaled species and placed the subjects in tank-like "travel machines" whose design was based on his own life-support chair.
Simplified: Davros experimented on living Kaled cells to find the ultimate mutated form of the Kaled species and placed the subjects in "travel machines" whose design was based on his own life-support chair.