Fact: Reactive Systems are taking over the world. Ever since the Reactive movement was well-defined in the www.reactivemanifesto.org libraries as well as entire organisations started embracing this concept. For example libraries like Play or Akka have been embracing the asynchronous nature of Reactive apps and messaging at their core for years. All in pursuit for a better way to build scalable, resilient and fast applications. One of the results of this are Reactive Streams, started out by Lightbend late 2013 which started out as a collaboration between a number of companies, and eventually ended up a part of the upcoming JDK9 release. In this talk we'll talk about what Reactive is, what aspects it has and how Reactive Streams (reactive-streams.org) is a great building block but not the whole story. Examples will be using Akka, but no knowledge of the library is required beforehand, and the concepts we'll talk about relate to software design in general, not only a single library.