Google tweaked their logo. It's nice. But it's not just a logo it's a design system or something. Here's more than you ever wanted to know about it, Evolving the Google Identity.
If this fascinates you, then you might want to back this Kickstarter campaign to Reissue the 1975 NASA Graphics Standards Manual. $79 will get you a hardbound copy of the 200 page document that introduced the "worm" logo, ahem, design system.