Back in 2011, Boeing initiated the 737 Max program, intended on providing a more fuel-efficient successor to the 737NG (-600, -700, -800, -900) family and competing with the Airbus A320neo (new engine option), which was announced a year before in 2010. After a rather quick development program, the first 737 Max prototype rolled out in December of 2015. Just yesterday, on January 29 2016, the 737 Max made its maiden flight from Boeing’s production plant at Everett, Washington to Boeing field in Seattle. The 737 Max will be offered in three variants: -7, -8, and -9 based on the -700, -800, and -900 variants of the 737NG family respectively. The prototype aircraft that made the maiden flight of the 737 Max was a -8, will be delivered to launch customer Southwest Airlines in 2017. The 737 Max supposedly incorporates many of the technologies found on the 787, including Boeing Sky Interior’s updated overhead bins and LED cabin lighting, as well as Rockwell Collins enhanced LCD screens for the flight deck and additional fly-by-wire control systems. The main improvement on the 737 Max are the CFM Leap-1B engines, designed to increase fuel efficiency by 10-12% in comparison to the 737NG.

More info on the 737 Max program: https://en.wikipedia.org/wiki/Boeing_737_MAX

Article on maiden flight of 737 Max: http://www.usatoday.com/story/travel/flights/todayinthesky/2016/01/29/boeings-new-737-max-takes-off-maiden-flight/79516468/