Liquid crystal blue phases have a fluid lattice whose structure is stabilized by cubic defects. Blue phases, which are classified as BPIII, BPII and BPI observed on cooling, exist over a small temperature range (ca. 1K) between isotropic and chiral nematic phases. Recently, we reported electro-optical switching with a response time of the order of 10(-2) s for the BPIII exhibited by a polar chiral T-shaped compound. We describe molecular design of a liquid crystal stabilizing a blue phase III, and discuss electro-optical switching in the blue phase.