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

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

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.