Early in the 21st Century, the Tyrell Corporation advanced robot evolution into the Nexus phase - a being virtually identical to a human - known as a Replicant. They're all around you, even now. That guy next to you? He's a Replicant. How do we know? He's walking the streets in the rain with no umbrella. That, and he failed the Voight-Kampff.
LED Umbrella
