The unsung heroes in the TYPO3 Universe are like background singers, they do a great job and are appreciated by everyone, but beyond the developer's world they are likely in the shadow of the bigger systems they are a part of.
Starting in 2009 with TYPO3 CMS 4.3 as a backport from the development branch of TYPO3 Flow (formerly known as FLOW3), extbase started to become the successor to the old pibase, the class all extensions derived from. Since then Flow has been perfectly integrated in the community and next to TYPO3 Neos of course is the center of the annual “Inspire” Conference.
TYPO3 CMS 4.5 LTS, the very first TYPO3 CMS version with Long Term Support, introduced "FLUIDTEMPLATE" as a new Content Element for using the Fluid Templating Engine. At that point in time Fluid, which was originally developed along with TYPO3 Flow, was about to become indispensable in the creation of future-proof extensions and website templates.
Both TYPO3 Flow and Fluid have proven stability and extensibility. Their support keeps the major products of TYPO3 future-proof and state-of-the-art; despite this the developers of Flow claim "it ain't rocket science"!
There is hardly any use in technology if it isn't used, so Surf is a great example of a tool that is powered by TYPO3 Flow. The Surf package is a completely automated deployment tool powered by TYPO3 Flow. It's best used for, but not limited to, deploying Flow applications. Development started in 2011 and it has since been used in deploying the flow.typo3.org and neos.typo3.org sites as well as numerous customer projects and T3CON Sites which are based on TYPO3 Neos.