MPs have voted in favour of proposals to legalise assisted dying in England and Wales.
The bill will now face many more months of debate and scrutiny by MPs and peers, who could choose to amend it, with the approval of both Houses of Parliament needed for it to become law.
It is also possible the bill could fall and not become law at all.
The bill - called the Terminally Ill Adults (End of Life) Bill - would make it legal for over-18s who are terminally ill to be given assistance to end their own life.
But there are requirements:
Under the bill, a doctor could prepare the "approved" substance (the bill does not detail what medication this is) but the person themselves must take it.
No doctor or anyone else would be allowed to administer the medication to the terminally ill person.
The doctor would stay with the person until they had self-administered the substance and died (or the doctor determines the procedure has failed).
The person could decide not to take it, in which case the doctor would have to remove the substance immediately.
Doctors would also not be under any obligation to take part in the assisted dying process.
This is called physician-assisted suicide. Voluntary euthanasia is different and is where a health professional administers the drugs to the patient.
Deaths covered by the assisted suicide bill would not need to be investigated by a coroner.
But the bill would make it illegal for someone to pressure, coerce or use dishonesty to get someone to make a declaration that they wish to end their life or to induce someone to self-administer an approved substance.
If someone is found guilty of either of these actions, they could face a jail sentence of up to 14 years.
The law would apply to England and Wales. A separate bill is already under discussion in Scotland.
Meanwhile, politicians in Jersey and the Isle of Man have already backed plans to introduce assisted dying and the process to bring in legislation is under way.