Although abundant in nature, the color blue is notoriously hard to create as a dye. In fact, the process behind indigo's transformation from parasitic shrub to precious stain is still only partially understood by scientists. Catherine E. McKinley tells the pigment's fascinating story here, winningly weaving into her historical researches a personal narrative illuminating her own tangled heritage, which has uncanny ties to the fabled hue.

July 24: On this day in 1725 John Newton, the slave trader-preacher who wrote the hymn "Amazing Grace," was born.

Crime fiction legends Dennis Lehane and Michael Connelly discuss the new book that unites their beloved sleuths Patrick Kenzie and Harry Bosch.