Experimental biology
Morgan earned his doctorate at Johns Hopkins and initially investigated morphology, development and regeneration. He became Professor of Experimental Zoology at Columbia in 1904 and later adopted fruit flies, which could be bred rapidly in large numbers, for genetic experiments.
References: [1]
Fruit flies and chromosomes
Crosses involving white eyes and other variant traits supported investigations of sex linkage, genetic linkage and crossing over. Sturtevant and other collaborators used recombination frequencies to order genes relatively, strengthening the chromosomal interpretation through several kinds of evidence.
The Caltech research group
Morgan moved to Caltech with longstanding collaborators in 1928, helping establish its biology programme. The 1933 Nobel Prize went to Morgan, while the research grew from a network including Sturtevant, Bridges, Muller and others.