She was best known for her research in limb regeneration, the role of the extracellular matrix (ECM) in cell differentiation, and epithelial-mesenchymal transitions (EMT).

Hay was thrilled by the introduction of transmission electron microscopy (TEM) during her lifetime, which aided her in many of her findings throughout her career.

When World War II began, her father, who was a practicing physician at the time, enlisted in the US Army Medical Corp.

During her sophomore year at Smith College, she began research on amphibian limb regeneration with Professor S. Meryl Rose, who became Betty's mentor and close friend.

[5] Betty's love for drawing pictures of slides and dissected animals are some of the experiences that cemented her aspiration to pursue a career in biology.

Soon after, Hay moved to New York City to work with electron microscopists at Cornell Medical College and the Rockefeller Institute.

[2] Hay is best known for her research in limb regeneration, the process of epithelial-mesenchymal transitions (EMT) during development, and the role of the extracellular matrix (ECM) in cell differentiation.

By transmission electron microscopy (TEM) they showed that the blastema that formed on the amputated surface of the amphibian limb contained uniform undifferentiated cells.

[7] In 1957, Don Fischman started as a medical student at Cornell and immediately joined Betty's laboratory due to his undergraduate experience of working with amphibian limb regeneration.

Hay needed his help in order to prove that the epidermis produced collagen, which was an idea that she and Jean-Paul Revel originally postulated.

[10] The second was using Nomarski optics to study how corneal fibroblasts migrated through the stroma in vivo and in collagen gels (a technique developed by JB and Tom Elsdale in Scotland).

[11] Gary Greenburg then entered Betty' lab as a graduate student, and they started working with 48-hour chick embryos.

He worked with Hay using TEM to prove that EMT removed the palatal seam that forms when the opposite shelves fuse.

She asserted that the basis of many scientific ideas originate from the full understanding the ECM's composition, relationship to the cell surface, and role in development.

Betty's work on revealing the role of ECM in regulating cell behavior led to her receiving over twenty national and internal awards.