Raised in Portland, Oregon, Milton Harris was a native of Los Angeles. As a youth, he worked in his parents' small mom-and-pop grocery store. By the time he was eleven years old, he was in the library reading through technical books whenever the family business permitted. His first independent business enterprise, at the age of twelve or thirteen, was building crystal radio sets. A high school chemistry course, taken soon after, increased his interest in the subject. Harris adamantly declared that at this point in his life he was extremely receptive to anything that was of a technical nature. Due to his influential introduction to chemistry, Harris became a strong advocate for the support of education and stressed the importance of technical training from an early age.

In 1924, at the age of sixteen, Harris began his college education at Oregon State University, then known as Oregon Agricultural College. During his three years at Oregon Agricultural College, Milton Harris was involved with a wide variety of programs on campus. These included: Phi Sigma Kappa, Freshman Tennis, Varsity Tennis, Interclass Basketball, the Circle "O" Association, Chi Epsilon (Local Honorary in Chemistry), and Tau Beta Pi (National Honorary in Engineering). Despite the lack of a chemistry department at that time, Harris pursued a degree in Chemical Engineering and took all of the available courses in chemistry. While a sophomore, Harris was called in to meet with his advisor, who told him that he had taken more chemistry courses than anyone at the University and that he was almost done with his course work. His advisor then told him about a twelve-week course in chemistry at the University of Washington that would allow him to graduate early. This advisor asked about Harris' future plans, to which Harris said that he would probably get a job, and that the only job he was aware of was an analytical chemist position in Portland at the gas company. His advisor told him that furthering his education by going to graduate school would probably be a good idea. Harris responded with a question: "What's a graduate school?"

At the age of 18, Harris graduated from OSU, and decided to attend Yale University. This was in part because a friend of his, Tom Hawley, was also attending Yale. After doing work on synthetics with Pete Johnson, Harris received a fellowship in biochemistry from the Cheney Brothers silk mills that allowed him to work with Professor Vickery. It was then that he became interested in protein chemistry and the structure of protein fibers. Upon his graduation from Yale in 1929, Harris took his first job as a chemist at the Cheney Brothers Mill, where Tom Hawley was also working. Harris was called away from Cheney in 1931 by Pete Johnson, then a member of the advisory committee for a textile industry group. Johnson wanted him to help start a new textile research group at the National Bureau of Standards. The National Bureau of Standards (NBS) was attempting to push industry toward innitiating widespread supportive research for its products. The NBS and the IF set up a program in which the Industry Foundation paid the salary of the researcher while the National Bureau of Standards provided the laboratory facilities. In Harris' opinion, since all of the research being conducted was of a "basic" nature, the program became a very exciting opportunity for him to broaden his knowledge. Immediately following his transfer to the National Bureau of Standards, Milton Harris began to summarize articles for Chemical Abstracts and was appointed editor of Section 25 on Dyes and Textiles, thus providing him with further opportunities to educate himself. During his brief time as a professor at Catholic University, Harris taught a course in polymer chemistry. He regularly spent ten to fifteen hours preparing for each two-hour lecture. Later, when the Industry Foundation consolidated their fellowships, Harris was appointed director of the research group. While at the National Bureau of Standards, Harris' research group produced approximately 200 scientific papers on various aspects of textile chemistry.

It was at the NBS that Milton Harris, along with Vincent duVigneaud, made his first big discovery. The men observed similarities between the three-dimensional molecular structures of wool, insulin, and human hair. They realized that all of these three-dimensional polymers are held together by cystine disulfide linkages. The hormone insulin is a protein with covalently connects polypeptide chains. Disulfide bonds holding these chains together with noncovalent forces are easily separable, and cystine is the product of oxidation between pairs of cysteine side chains that form a disulfide bond. The presence of these disulfide bonds in cystine proteins often plays an important structural role. Disulfide bonds, while relatively rare, are found primarily in proteins exported from cells. When disulfide bonds are reduced the protein unfolds, but upon reoxidation these disulfide bonds are reformed, which is an unexpected reformation. In the reoxidation, cysteine bonds are formed, which, given time, oxidize into the disulfide bonds in a cystine protein, thus providing a more stable structure. Hair consists of a fibrous protein called keratin, which contains an unusually large number of disulfide bonds. To straighten or curl hair, a reducing agent is used, which temporarily dissolves the disulfide bonds. After the hair has been curled or straightened, an oxidizing agent is used to reform the disulfide bonds. Since these disulfide bonds are no longer in their original position, the hair holds its new shape.

With the advent of the U.S. involvement in World War II, Harris' group began advising the Army Quartermaster about textiles, as well as helping to solve a myriad of problems for the National Bureau of Standards. George Dorio, a Frenchman from the Harvard Business School, was recruited to run the Research and Development Branch of the Office of the Quartermaster General. According to Harris, Colonel Dorio called him one Sunday morning and immediately requested his presence at the Pentagon. Upon Harris' arrival, Colonel Dorio pulled out some cotton underwear from a box. Almost immediately the underwear disintegrated. Colonel Dorio wanted to know why this had occurred. They soon found out that the cotton which comprised the garment had been treated with chemicals against gas warfare, and in the process hydrochloric acid had been liberated which led to the deterioration of the fabric. Since Harris had already been working on the degradation of cellulose by various methods, Dorio had him start work on this new project the next day.