The COP21 negotiations are entering their final hours here in Paris - the culmination of 20 years of work by successive generations of national governments, activists, scientists and others.
The draft text presented last night by French ministers has a lot of agreement, and there is a lot of progress in setting targets and outlining ambitions to tackle climate change.
It's an impressive document and has confounded those who thought Paris would be a bust.
But there are still many hard decisions for countries to make.
On the table is an agreement to limit the future rise in global temperatures "well below" 2C by the end of the century. And the world will "pursue" an even stricter target of 1.5C.
That target will please vulnerable small island nations, which already suffering the creeping impacts of climate change - droughts, sinking shores and storms.
Neither target will be easy. To do it, the draft agreements says the world has to reduce its greenhouse gas emissions to zero overall by 2050. That means anyone emitting greenhouse gases after this point has to work out a way to suck it out of the atmosphere - whether that's carbon capture and storage, planting lots of trees or some (as-yet-unknown) future technology.
But there's plenty still to work out.
One point of contention is a proposal to redefine which countries are classed as "developed" and "developing".
For the UNFCCC (which convenes COP21), that distinction was made more than 20 years ago, when the world was a very different place. China hardly compared to the West when it came to greenhouse gas emissions, whereas now it is the world's biggest emitter.
In the UNFCCC process, developed countries have to take more responsibility to cut emissions and pay for developing nations to invest in clean technology.
The Paris agreement has language in it to try and blur the hard line between developed and developing nations with lots of shades of grey in between them. Many countries, notably led by India won't be happy with the extra burdens that may come with a change in designation.
And who pays for everything? Poorer countries say they need to spend trillions of pounds to adapt to future climate change and invest in clean energy technology to bring their people the basic needs we all enjoy in the richer countries. But only £65 billion per year from 2020 is on offer from rich countries and the poor want bigger commitments.
In return, many rich nations want a "ratchet" mechanism in the agreement, which would require countries to re-visit (and accelerate) their commitments to cutting emissions every few years.
Many developing nations are resistant to that, since they don't want to get potentially locked into a legally-binding brake on their future economic growth.
Despite these bones of contention, there's lots of optimism in the delegates at COP21 that a deal will be done on Saturday.
One notable factor in these talks has been that, as well as the negotiating on the ground here, President Obama has been on the phone regularly to China's President Xi and India's Prime Minister Modi and many others, in order to try and push the deal forward at the highest levels.
The French ministers leading the Paris talks will continue to work through tonight to prepare and present a new version of their agreement in time for Saturday morning.
Only then will we find out who's compromised what in this historic deal to save the world.