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.

Example Input: Fact 1: when a plant grows , the size of the leaves of that plant may increase. 
Fact 2: Leaves are the main sites of photosynthesis.
Example Output: when a plant grows the main site of photosynthesis increases in size.

Example Input: Fact 1: increasing heat causes thermal expansion. 
Fact 2: Motion helps to increase body heat.
Example Output: motion causes thermal expansion.

Example Input: Fact 1: Cells vary in size as well as shape, but all cells are very small. 
Fact 2: An embryo is so small that it requires a microscope in order to be seen.
Example Output:
A cell requires a microscope in order to be seen.