A volcanic eruption in what’s now Morocco preserved ancient trilobite specimens in nearly pristine condition about half a billion years ago, according to a new study.

In contrast, trilobite size was strikingly correlated with fluctuations in marine redox (i.e., marine oxygen levels), especially during the well-known anoxic events of this interval.

The four stages of hair growth are anagen, catagen, telogen, and exogen. Each phase has its own timeline, which can be affected by age, nutrition, and overall health. Learn more.