In 1963, the assassination of John F Kennedy shocked the world, but it also illustrated to American politicians that their constitution wasn't built for such events. That was until the creation of the 25th Amendment.
Ratified in 1967, the now fifty-year-old legislation is a small but vitally important part of the US constitution.
The amendment came about when Congress was looking for a better way to succeed presidents and vice presidents when they became ill or died.
It ensures that if the president dies there is a smooth transition of power to the vice-president. Similarly, if the vice-president is incapacitated, it details how to find a replacement.
What the act enables a president to do is temporarily cede power if they unable to lead or do their job.
The assassination of Kennedy jolted Congress into action and in 1967, the 25th Amendment was set into the US constitution.
It has been invoked on several occasions since that point including the resignation of Nixon, the shooting of Reagan, and when both Bush presidents underwent operations.
The amendment exists to act as a check should a president become no longer suitable for the position.
This happened in 1987 when officials were considering using the act against Ronald Reagan because he was allegedly "inattentive, inept", and "lazy".
This later proved not true, but now the amendment has become very popular with people suggesting it could be used against Donald Trump.
Some on social media believe that the behaviour of Trump means that the act should be used against him.
Despite this, it is highly unlikely that any action will be taken. However, there are plans by Democrat Jamie Raskin to introduce a bill on clarifying how a president could be declared medically unfit.