The Lewises developed a growth medium called the Locke-Lewis solution and jointly received the Gerhard Gold Medal from the Pathological Society of Philadelphia.

At Bryn Mawr and Columbia she researched regeneration in amphibians and crayfish, and assisted noted embryologist Thomas Hunt Morgan.

[2][3][4] In 1908, Margaret Reed researched in Berlin in Max Hartmann's lab where she performed probably the first in vitro mammalian cell culture with guinea pig bone marrow by explanting the bone marrow and placing it into a nutrient-rich agar produced by fellow lab researcher Rhoda Erdmann and incubating the sample.

Since the Lewises main interest was microscopic cell structures, their objective was to create optically clear media, which led to the creation of the Locke-Lewis solution.

In the Locke-Lewis solution, the more robust cells, such as fibroblasts and macrophages, had a tendency to migrate out of the explant and flatten, making them easy to observe under high magnifications.

As a result, this couple's greatest impact on embryology and cell biology in the twentieth century was teaching later generations of biologists the basic factors involved in tissue culture based on what they had learned from their research.

With so many avenues opened by cell culture to explore, Margaret Lewis and her husband diverged in their area of study, with Margaret Lewis choosing to focus on microbiological problems, which involved close observations of chick embryo intestines reacting to typhoid bacilli in the medium in which it was grown.

[10] Some of Margaret Reed Lewis’ research in the mechanics of cancer included myeloid infiltration and strangulation-induced atrophy of tumors in rats.

[11][12] In her study on myeloid infiltration, Lewis found that this phenomenon occurred in the adrenals but was not common to all subjects tested with tumors.

[5] As a female scientist in the early twentieth century, Margaret Reed Lewis was not able to push her own achievements in her field of work, but she with her husband was able to further develop tissue culturing techniques and demonstrate how single cells impacted the organism as a whole.