Plans for a Test championship and one-day international league have been approved by the International Cricket Council.
Nine teams will play six series of Test matches over a two-year period - three at home and three away - culminating in a world Test championship final.
A 13-team ODI league, introduced from 2021, will now be used to qualify for the World Cup.
The ICC has also given the go-ahead for a trial of four-day Test matches.
"Throughout the discussions about the future of Test cricket it became clear that we must also consider alternatives and trial initiatives that may support the future viability of Test cricket," ICC chief executive David Richardson said.
How would the Test championship work?
The Test competition, which will begin after the World Cup in 2019, is designed to increase interest in the longer form of the game and avoid one-sided affairs.
There will be a minimum of two matches in each series - all of which will be scheduled to last five days - but can be expanded to five for series such as the Ashes.
The top two teams by April 2021 will then play in a championship final in England.
Zimbabwe, Afghanistan and Ireland would initially be excluded from the Test championship but the introduction of four-day series would give them more Test experience.
A Test league has been mooted for years, with Richardson saying in 2016 that a league would help "create a real champion Test team".
Day-night Tests have been introduced in an attempt to boost attendances.
And what about four-day Tests?
The trial for four-day Test matches will run up until the World Cup, which will be hosted by England.
South Africa recently requested to play a four-day Test against Zimbabwe in December, before their three Test series against India in January.
"Four-day Tests will also provide the new Test-playing countries with more opportunities to play the longer version of the game," Richardson continued.
"It will, in turn, help them to hone their skills and close the gap with the top-nine ranked teams."
Ex-England captain Charlotte Edwards, speaking on BBC Radio 5 live
I think four-day Tests are something they have got to try but the purist in me would like to see five-day Tests continue.
Anyone who is watching the Ashes series this winter will want them to continue as five-days. I think there's a place, potentially, for four-day Test cricket and it's great that the ICC are looking into that.
I think the future of the game looks bright in any format, which is the most important thing.
How would the ODI league affect teams?
The top seven one-day sides currently automatically qualify for the World Cup, with a qualifying tournament held for the lower-ranked sides.
The new league would see the top-13 teams play eight series lasting three matches over three years.
"Bringing context to bilateral cricket is not a new challenge, but this is the first time a genuine solution has been agreed on," ICC chairman Shashank Manohar added.
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