Room, also known in Japanese as "ルーム" (Rūmu), is the basic technique which Trafalgar D. Water Law uses in the popular manga and anime series One Piece. This ability serves as a foundation of Law's powers from Ope Ope no Mi, a red, heart-shaped fruit that is reminiscent of a strawberry. Room is a spherical space, an umbrella technique on which all his other powers are based, where he can basically control anything and everything.
When Law activates Room, he centers an area-of-effect area on himself and his targets. This allows him to treat objects and living beings in the space around him like he would while performing surgery. The appearance of Room often takes the form of a light blue, transparent sphere in the anime that encapsulates its area of effect. It's worth mentioning, however, that whereas the edges of the Room are very clear, in some cases there is no obvious indication as to whether the ability is active or not within the confine.
Room's most salient feature is probably its versatility—Law can turn it to any purpose, whether in the realm of offense or defense, or even non-combat applications. One of Law's signature moves with Room is the "Shambles" ability, allowing him instantly to switch the positions of any objects or people inside Room. With his ability to change the battlefield in real time, Law becomes an unpredictable, formidable enemy.
Since Law has grown in power through the series, he eventually worked on variations focusing on the basic Room technique. One of these advanced versions is "R-ROOM," which stands for "Remote Room." This tech gives a much more stable Room with an orbital aura. Applied on a target, it gives Law the ability to manipulate them remotely, further extending his ability's range and versatility.
The visual impacts of Room have turned it into a One Piece fan favorite. Across several social media sites, there are plenty of fan arts or edits or, at times, simple discussions solely based on the technique. Starting from Law turning on Room to the often-coming tagline of "Room," the visual has become a very iconic moment in the series and something the audience looks forward to in the battles of Law.
It must be noted, however, that Room also has its limits: it costs quite a lot of stamina to have Law hold a huge Room for too long. In addition, the size of the Room depends on the condition and situation of Law; larger Rooms consume more energy to hold. The energy meter and limited size of the Room introduce an element of strategy to Law's fights, since he must wisely conserve his energy while keeping it large enough to be useful.
Throughout the series, Law has used Room in many memorable fights. One such instance was during the Punk Hazard arc, where he used Room to switch the personalities of Marine Captain Tashigi and Vice-Admiral Smoker, unveiling the potency of the technique in confusing enemies. This not only presented Room as a versatile tool but also opened up some very interesting questions regarding the extent of Law's powers in his sphere of influence.
Mastery over Room and the powers that it enables have earned him the nickname "Surgeon of Death," which has its origins in his profession as a doctor, reflecting the surgical accuracy with which he can manipulate anything within his Room. This combination of knowledge about medicine and powers from the Devil Fruit makes Law a very unique character in the universe of One Piece.
With the continuation of the One Piece saga, it is very much anticipated that the Room technique would be further developed or applied by Law in future storylines. Having special properties to the ability and how Law used it with much creativity really makes the ability a stunning feature of the vast and intricate world of One Piece.