Microsoft's Aero Glass on Windows Vista introduced UI design that showed content behind windows through blurred translucent borders. Windows 7 built on the look, but

In case you missed it, Apple has caught quite a volley of criticism for what’s perceived as making it seem like Liquid Glass has reinvented the idea of transparency – a glassy, see-through interface – when this was actually done by Microsoft in… yes, you guessed it: Windows Vista.

Microsoft has officially poked fun at Apple's Liquid Glass UI overhaul by sharing images of an old Windows operating system version.