Last month, Twitter introduced Twitter Developer Labs, a program where developers can test and provide feedback on new API features. The first two endpoints under the Twitter Developer Labs program are now available. GET/users and GET/tweets are now available. Through the endpoints, developers can look up users or retrieve tweets based on a user's ID.
If you visit the Twitter Developer Labs site, you will notice that Twitter includes a roadmap that shows API features that are currently available through the program, and what is soon to come. Accordingly, the https://api.twitter.com/labs/2/users and https://api.twitter.com/labs/1/tweets endpoints listed as now available while Filtered Stream and Recent Search are scheduled for the future.
The new features available through the GET/users and GET/tweets endpoints include the ability to customize data returned for each request, a simplified endpoint structure, and some API updates that developers have requested. For more details, check out the Twitter Developer Labs docs.
All APIs and endpoints released under the Twitter Developer Labs program are in the preview stage. This applies to new APIs, formats, expansions, versioning, and features. Those interested can always see what's new in the changelog. For access to the Developer Labs program, apply here.