Renaissance artists prepared pigments through a meticulous process that involved grinding natural minerals, plants, and sometimes even insects into fine powders. These raw materials were sourced from various parts of the world, making some pigments extremely valuable. For example, lapis lazuli was imported from Afghanistan to make ultramarine, one of the most expensive pigments. After the initial grinding, artists mixed these powders with a binding agent, such as egg yolk for tempera paint or linseed oil for oil painting, to create the desired consistency and adherence for application on surfaces like wood panels or canvas. This period marked a significant advancement in artistic techniques, including the development of new pigments and the perfection of color blending and shading, enhancing the realism and depth of their artwork. The preparation of pigments was not just a scientific task but an art form in itself, requiring knowledge, patience, and skill.

A polypeptide is not an amino acid, but rather a chain of amino acids linked together by peptide bonds. Amino acids are the building blocks of proteins and polypeptides. When several amino acids join in a chain, they form a polypeptide, which can then fold into a specific shape to become a functional protein. The structure and function of proteins depend on the sequence and arrangement of these amino acids in polypeptides. Therefore, while a polypeptide is closely related to amino acids as their polymer, it is a distinct biological entity involved in forming the structure and executing the functions of proteins within organisms.

A unit of yarn is traditionally called a "skein." Skeins are how yarn is commonly sold, consisting of loosely coiled lengths that are easy to manage and prevent tangling. When buying yarn, it's common to find it labeled by weight and length, information that's especially vital for specific projects like knitting or crocheting. Skeins make it convenient to work directly out of the packaging, pulling the yarn end through the center or from the outside. Besides skeins, yarn can also be wound into balls, hanks (which are loops of yarn twisted into a coil), and cakes (cylindrical shapes with a flat top and bottom), each with its advantages for storage and use. The choice between these forms depends largely on preference and the specific requirements of the project at hand.