So you want to have the smallest to the point of the microscopic level OS there is. Well, as derived from its title, Tiny Core Linux is indeed incomprehensibly the smallest OS available with at 11 MB as a text console and 16 MB of GUI. It’s perfect for resurrecting old computers with minimum resources, network boot photos, or images and to any user who just wants to have more softwares and applications storage space than its operating system. You can use Etcher to install this operating system. You can follow this link to get it.
And yes, it does run seamlessly as tested on a 128 MB thumb drive on 512MB RAM, after all the OS only takes 16 MB of space. It might have a slow performance when it comes to navigating the internet using a browser, but whose fault to blame lies on the complexity of websites instead of Tiny Core. It runs without GUI, just by 64MB RAM. For instance, you might want to recover some files or fix your boot partitions, as other lightweight Linux Tiny Core can also do the job, aside from saving old computers. If you do decide this one, you have to know it only comes with a text editor and terminal, you need to install or add a few applications, this is where the Apps icon does its role. It has the features you need on which package to install, mostly server-centered, graphic and office installation and user-friendly applications.