src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<Notification<T>> materialize() {
        return RxJavaPlugins.onAssembly(new ObservableMaterialize<T>(this));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<Notification<T>> materialize() {
        return RxJavaPlugins.onAssembly(new ObservableMaterialize<T>(this));
    }
Returns an Observable that represents all of the emissions <em>and</em> notifications from the source
ObservableSource into emissions marked with their original types within {@link Notification} objects.
<p>
<img width="640" height="315" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/materialize.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code materialize} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@return an Observable that emits items that are the result of materializing the items and notifications
of the source ObservableSource
@see <a href="http://reactivex.io/documentation/operators/materialize-dematerialize.html">ReactiveX operators documentation: Materialize</a>
@see #dematerialize(Function)