The new-look Champions League draw will be held on Thursday from 17:00 BST and you can watch it live on the BBC Sport website.
Teams will discover which eight clubs they will meet (four at home and four away) – but no actual groups will be drawn.
All the teams will be in one 36-team league phase, as compared to the past format of eight four-team groups.
So how will the draw work?
Team will be placed in four pots according to their seeding. Each team face two teams from each pot, one at home and one away.
A team will be drawn out of a pot and then Uefa’s software will decide their eight opponents – and whether they will be at home or away.
It means more matches between the biggest teams. For example, Manchester City could face Real Madrid, Bayern Munich and Barcelona.
The software stops teams playing rivals from their own country – and means each team can only play two clubs from any one country.
Uefa says the computer system plans ahead so will ensure no teams further down the line get drawn against teams they cannot face.
How does the new format work?
Teams who finish in the top eight will qualify automatically for the last 16, while those who place ninth to 24th will compete in a two-legged knockout play-off for the chance to join them.
Whoever finishes 25th or lower will be eliminated and will not be entered into the Europa League.
From the last 16 onwards, the Champions League will continue to follow its existing format with the final taking place at a neutral venue – Munich this year.
The number of matches in the new format will increase from 125 to 189.
Each team will play a minimum of eight – instead of six – and a maximum of 17.
The league phase will now run until the end of January instead of ending before Christmas.
Who is in the draw?
England: Man City, Arsenal, Liverpool, Aston Villa
Spain: Real Madrid, Barcelona, Girona, Atletico Madrid
Italy: Inter Milan, AC Milan, Juventus, Atalanta, Bologna
Germany: Bayer Leverkusen, Stuttgart, Bayern Munich, RB Leipzig, Borussia Dortmund
France: Paris St-Germain, Monaco, Brest
Netherlands: PSV Eindhoven, Feyenoord
Portugal: Sporting Lisbon, Benfica
Belgium: Club Bruges
Scotland: Celtic
Austria: Sturm Graz, Salzburg
Ukraine: Shakhtar Donetsk
Switzerland: Young Boys
Czech Republic: Sparta Prague
The final four slots will be determined via the play-offs on Wednesday night.
Source: BBC
