The Steriod nucleus
Steroid refers to the group name for lipids that contain a hydrogenated cyclopentanoperhydrophenanthrene ring system.
(10R,​13R)-​10,​13-​dimethyl-​17-​(6-​methylheptan-​2-​yl)-​2,​3,​4,​7,​8,​9,​11,​12,​14,​15,​16,​17-​dodecahydro-​1H-​cyclopenta​[a]phenanthren-​3-​ol
Without simplification, lipids are composed of One acid head and One hydrocarbon tail. Lipids are found in two main classes: Oils are from Plant sources and are liquid at room temperature [dog-legged unsaturated lipids - they stack like broken toothpicks] while Fats are from animal sources and are solid at room temperature [straight chained saturated lipids - they stack easily and solidly like straight toothpicks]. With Elemental simplification; Carbon and Oxygen are in the Acid, with Carbon and Hydrogen [and the occasional C=C double unsaturated double bond or two] are in the Tail. Tail monomers are -CH2- there may be anywhere from 13 of these monomers up to 28 of them!