As I said earlier, a common theme in biology is how large "macromolecules" from subunits, usually known as monomers.
Proteins are arguably the most important and, inarguably, the most diverse of all the macromolecules.
Each protein begins as a long strand of hundreds (or thousands) of amino acids. Since there are 20 different amino acids commonly used, 100 amino acids would have 20100 possible sequences.
In practice, you won't see all possible ones and they are not randomly put together. Instead, the information in the DNA is used to specify what sequence is made (through a process we will learn about).
These chains then fold into complex structures you have seen.