Telegram is an increasingly popular messaging app thanks to its focus on security and the free price tag. An alternative client called Challegram popped up a while back, and now the developers of Telegram have acquired it and changed the name to Telegram X. It includes all the basic messaging features from the regular Telegram app, but there are a few experimental features, too.
Telegram X is built to be noticeably faster and smoother than the main Telegram app—the animations are really impressive. You can also long-press on conversations to get a pop-up preview. Night mode? That's included in the app as well. The text size is also fully configurable.
The original Challegram app acquired by Telegram was based on the open TDLib (Telegram Database Library), but it's not alone in that respect. The devs must have seen something special in this client to snap it up. It's already excellent, but maybe it'll become the main Telegram app some day. For now, you can install Telegram X and log in with your existing account to give it a shot.