#cmothart

Their skin is made of either silicone rubber, or a substance very similar to it, so it’s pretty heat resistant (good when your species used to frequently re-enter the planet’s atmosphere after lunch from a nearby asteroid). It's also more resistant to rips and tearing. 

Then you have their sensory/nervous system. Inside their body, it’s a semi-liquid black goo, and hardens into a gel outside (like their eyes). Visible here is mostly just the layer below their skin that senses touch, heat, and EM fields, but its  present practically everywhere. 

The next few layers vary depending on the body part, but usually you’ll have at least some section of material/reserve storage (to use in shapeshifting, healing, and replenishing their generator) that also houses blood pathways and other organs. Speaking of blood, cores only need oxygen as fuel for their furnace stomachs when they are digesting, so they don’t just have blood going everywhere in their body, and the ‘veins’ are also by default closed and empty.  They have a little pouch beside their stomach where they keep some oxygenated blood. Their ‘blood’ is also used to help carry additional materials to the needed sites when healing or shapeshifting. It’s clear or light pink in their body, and amber gold when oxygenated. 

What is very important to their frame’s upkeep is their electrolyte gel: it’s what moves current and voltage from their core around their body. It’s surrounded by various layers of materials that serve as electrodes and regulators. 

Finally, the grey/metallic parts are their frame’s support and movement systems, providing both the actual ‘skeleton’ and the actuators and hydraulics that move it. They’re very similar looking, and cores don’t really have a notion of separate ‘muscles’ and ‘bones’. For flexible things like antennae or grasping limbs/tentacles, hydrostatic semi-liquid metal ‘muscles’ are used.