Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.

Fact 1: Steroid hormones are made of lipids, such as phospholipids and cholesterol. 
Fact 2: Lipids Lipids are diverse hydrophobic molecules.
Steroid hormones are made of diverse hydrophobic molecules, such as phospholipids and cholesterol.

Fact 1: Scientists who find and study fossils are called paleontologists. 
Fact 2: Fossil fuels are the fossilized remains of prehistoric animals and plants.
paleontologists study the remains of plants.

Fact 1: Muscle contraction occurs when muscle fibers get shorter. 
Fact 2: Contraction of the muscle straightens the leg.

The leg straightens when muscle fibers get shorter.