654877bd_erials_Science_and_Engineering__Significance
[Date] 1890 [Candidate Moment] Adolf Martens examines the microstructure of a hard steel alloy and finds that, unlike many inferior steels that show little coherent patterning, this steel had many varieties of patterns, especially banded regions of differently oriented microcrystals. [Significance] 
Initiates the use of microscopy to identify the crystal structures in metals and correlate these observations to the physical properties of the material.