Volume 542 Number 7640



News Features

Secrets of life in a spoonful of blood p.156

The intricate development of the fetus is yielding its long-held secrets to state-of-the-art molecular technologies that can make use of the mother's blood.

doi: 10.1038/542156a

News & Views

Interspecies pancreas transplants p.168

A mouse pancreas grown in a rat controls blood-sugar levels when transplanted into a mouse that models type 1 diabetes. This achievement provides a tantalizing glimpse of how organs could be grown for therapeutic use. See Article p.191

doi: 10.1038/nature21490

Ocean circulation drove increase in CO2 uptake p.169

The ocean's uptake of carbon dioxide increased during the 2000s. Models reveal that this was driven primarily by weak circulation in the upper ocean, solving a mystery of ocean science. See Letter p.215

doi: 10.1038/542169a

Tiny fossils in the animal family tree p.170

Newly discovered microscopic fossils might shed light on the early evolution of the deuterostomes, the animal group that includes vertebrates. But more work is needed to resolve the fossils' place in the deuterostome tree. See Letter p.228

doi: 10.1038/nature21493

Dark matter remains elusive p.172

WIMPs, or weakly interacting massive particles, are the leading candidates for dark matter, the 'missing' mass in the Universe. An experiment has obtained no evidence for such particles, despite an impressive increase in sensitivity.

doi: 10.1038/542172a

In search of lost time p.173

Electrical stimulation of the human brain does not enhance memory, according to a report that is in apparent conflict with earlier work. But this discrepancy could enable deeper insight into brain dynamics by stimulating basic research.

doi: 10.1038/nature21497

Organelle formation from scratch p.174

Cellular organelles called peroxisomes aid metabolism, and defective peroxisome formation can cause disease. It emerges that peroxisomes can form de novo from the fusion of vesicles derived from two distinct organelle types.

doi: 10.1038/nature21496

Intermediate-mass black hole found p.175

The existence of medium-sized black holes has long been debated. Such an object has now been discovered in the centre of a dense cluster of stars, potentially enhancing our understanding of all black holes. See Letter p.203

doi: 10.1038/542175a



Interspecies organogenesis generates autologous functional islets p.191

The authors inject mouse pluripotent stem cells into pancreatogenesis-disabled rat blastocysts and thereby generate rats with mouse pancreata from which the islets, when transplanted into mice, can provide a long-term cure for symptoms of diabetes, without continuous immunosuppression.

doi: 10.1038/nature21070