Editing Breen (section)

==Physiology==

Breen physiology is among the most exotic for humanoid lifeforms, which may be due, in part, to their homeworld's climate. The Breen have no blood or other liquid circulatory system. The Breen brain is structured into four lobes; this protects them from the probing of some empathic species, such as the Betazoids, who are unable to detect the thoughts or emotions of the Breen. (DS9: "In Purgatory's Shadow"; TNG: "The Loss")

Breen appear physically more resilient than most humanoids. When Worf struck a Breen, the Breen proceeded to incapacitate Worf with a neural truncheon, seemingly oblivious to the assault. (DS9: "'Til Death Do Us Part")

It is possible this toughness was due, in part, to the Breen's armor rather than its physiology. 

The Breen constantly wear refrigeration suits in order to maintain a cold temperature like that on their homeworld. According to Worf, no outsider had ever seen what a Breen looked like under their refrigeration suits and lived. Even after joining the Dominion, their appearance was unknown to their new allies. Weyoun couldn't help but wonder what they looked like. (DS9: "Indiscretion", "'Til Death Do Us Part", "What You Leave Behind")

In "Indiscretion", Kira and Dukat don Breen suits, and Kira also wears one in "What You Leave Behind". It is likely that they killed Breen and took their suits for these disguises, suggesting they saw the Breen unmasked in the process. Worf's statement, however, may indicate that the Breen have another suit underneath, preserving the mystique of their appearance. 

Although it is often stated throughout the franchise that the Breen homeworld is a "frozen wasteland", Weyoun claimed the planet had a temperate climate, leaving one to wonder if the suits they wear are in fact to keep them cool. (DS9: "The Changing Face of Evil") However, the Cardassian Union was known at times to keep an embassy on the Breen planet, giving Cardassians knowledge of that world, and they did describe it as extremely cold. (DS9: "Return to Grace") Quark even compared Odo to being as "cold as a Breen winter". (DS9: "Crossfire") It is possible that the Breen created an elaborate deception to outsiders as to the true nature of their world, only revealing its true nature to their allies the Dominion or Weyoun was employing some sort of ruse.