Here's your 10-point cheatsheet to this big story:
Uddhav Thackeray will be sworn in as the new Chief Minister at Shivaji Park, a traditional venue for Shiv Sena events including founder Bal Thackeray's Dussehra rallies. Maharashtra will have a Sena chief minister after 20 years but a Thackeray as Chief Minister for the first time. In the election last month, Uddhav Thackeray's son Aaditya became the first of his family to ever contest the election.
Mr Thackeray will get just one deputy, from the NCP, the alliance has decided. NCP's Praful Patel announced on Wednesday evening that the Assembly Speaker's post will go to the Congress and the Deputy Speaker will be from the NCP.
Congress president Sonia Gandhi, her son Rahul Gandhi and former Prime Minister Manmohan Singh will not be attending the oath ceremony. Uddhav Thackeray's son and first-time MLA Aaditya Thackeray had flown to Delhi on Wednesday evening and met Mrs Gandhi and Dr Singh separately to invite them.
The Sena has also invited West Bengal Chief Minister Mamata Banerjee, DMK president MK Stalin, Delhi Chief Minister Arvind Kejriwal and nearly 400 farmers from various districts of Maharashtra for the swearing-in ceremony. Mr Kejriwal has reportedly said he won't be able to make it for the ceremony.
Around 2,000 policemen will be deployed at the Shivaji Park in Mumbai's Dadar for the 6:40 pm swearing in.
On Wednesday morning, newly-elected MLAs were sworn in more than a month after the Maharashtra election, in which no party won a majority. The Supreme Court had ordered the Governor to arrange their oath immediately and appoint a pro-tem or interim Speaker to oversee the proceedings. Interim Speaker Kalidas Kolambkar is overseeing the oath ceremony.
Uddhav Thackeray will have to become a member of the Maharashtra Assembly or the Legislative Council within six months of taking oath as Chief Minister. Sources say the Sena chief, who has never contested an election, is likely to take the Council route.
Devendra Fadnavis resigned on Tuesday after the Supreme Court ordered him to prove his majority by Wednesday. Ajit Pawar, who had failed to make good on his promise of pulling in NCP MLAs to help the BJP reach a majority, quit soon after.
Ajit Pawar's overnight switch had enabled a stunning early morning government formation by the BJP on Saturday, hours after the rival alliance had announced its intentions to take power. Ajit Pawar had been present at the Sena-NCP-Congress meetings but was seen taking oath with Devendra Fadnavis.
The BJP, which won 105 seats in the 288-member Maharashtra assembly, needed 40 more MLAs to prove a majority. The party had banked on Ajit Pawar to bring in 54 NCP MLAs, but the gamble didn't pay; hardly anyone followed "Ajit-Dada" and remained with NCP chief Sharad Pawar.