During their forty years of isolation, the Cylons developed or evolved into a humanoid form. Humanoid Cylons are visually indistinguishable from humans, down to the cellular level, but not completely at a molecular level. They mimic human form so completely that they are nearly undetectable to current Colonial technologies. 

There are twelve models of humanoid Cylons, representing twelve personality archetypes that the Cylons have witnessed in humanity and are responsible for masterminding the complete destruction of the Twelve Colonies through their use of sabotage and infiltration. Seven models have been identified. The identities of the final five remaining Cylon models are unknown to both humanity

and the seven known models. The creation of the humanoid Cylon is purely speculative. The original Cylon, a sentient robot, is likely to have had a major, if not a sole role in the creation of the humanoid forms. No concrete evidence exists as to when the first humanoid models were created and how long they have been among the human population. There is also no evidence as to whether all the 12 models were created at once or whether they were created at different times during the forty year exile.

Each humanoid Cylon has the same face, stature, hair, eye and skin color, gender, and other biometrics as all the others of his or her model. This point technically makes each copy a twin of itself, but there are some models that choose to make cosmetic differences. As well, each copy appears to start with the same basic personality, but each personality grows more distinct due to their individual experiences. They are susceptible to the same emotional traumas and joys that their human counterparts are, further proving that personalities are a realistic part of their psyche. The specific number of copies per model has not been specified. There appears to be no significance to any of the specific numbers assigned to the different Cylons.

Humanoid Cylons have the capacity to emulate many human physical acts, including sex. They also display convincingly human personalities (affection, jealousy, sadness, anger, sense of humor, religious faith etc.) This behavior continues even when interacting with other Cylons outside of Colonial scrutiny, clearly establishing that their personalities are genuine. 

Humanoid Cylons can be programmed as 'sleeper agents', who appear to have a low-level Cylon personality that can conduct operations while placing the human sleeper personality "on-hold."

Humanoid Cylons can dream, a process that appears to be natural to them.

Their psychology is based on what they simply refer to as "projection". Essentially an enhanced form of a self-induced and controlled hallucination, projection is how they choose to see the world around them, in any form they wish, whenever they wish. For example, if a Cylon were standing in a hallway, they could choose to see it as a forest filled with birds, trees, and sunlight. This mode of visualization is pleasing to agents. 

Some or all Cylon female models may have the capacity to bear children seeded by human males. The Cylons tested numerous methods of sexual reproduction, yet these failed due to a known flaw in their design. Humanoid Cylons cannot reproduce with each other biologically, so in an attempt to subvert this deficiency, they try to interbreed with humans, creating hybrid offspring.

The bodies of humanoid Cylons sometimes appear to have tremendous stamina and strength, and appear to be designed to destroy or resist commonly dangerous human diseases, although they are not immune from all contagions. In keeping with their desire to be a better human, however, the Cylons did not or could not further improve on other characteristic design flaws of the human body. Humanoid Cylons are heavily fortified to resist damage from intense radiation fields that would kill a human after short exposure, but they are still susceptible to damage from certain types of radiation or trauma. Despite their resistance to certain forms of energy, Humanoid Cylons, unlike the Cylon Centurion, cannot be made "bulletproof".

The majority of the Cylons follow a monotheistic religion. 

Upon the death of its body, a humanoid Cylons transfers its consciousness into another copy of itself. This "resurrection" is limited by distance, signal integrity, and proximity to the Cylon homeworld or a Resurrection Ship. 

It appears that all humanoid Cylons share a collective knowledge base of data from other active or deactivated humanoid Cylons, regardless of their model.

Humnanoid Cylons can interface with Colonial mainframe computers and communication systems by fiber-optic link. Although they cannot do so remotely or wirelessly, Humanoid Cylons can interface with Cylon computer systems or computer networks by photo-electronical means. They can perform this through subdermal physical contact if required or, preferably, through a Cylon data port. This might be possible through the use of bio-luminescent and photosensitive cells in their hands. The presence of a water-like fluid as an integral part of the basestar, the ability to interface photo-electronically through subdermal and dermal contact, and the fact that humanoid Cylon are anatomically indistinguishable from human beings, implies that the techniques used in their creation are advanced enough to incorporate cybernetic functions into their design without the use of specific internal structures other than human-like organs.