COVER A survey of cell types across tissues as part of the Human Cell Atlas, mapped with single-cell transcriptomics in three papers in this issue, lays the foundation for understanding how cellular composition and gene expression vary across the human body in health, and for understanding how genes act in disease. See pages See pages 695 and eabl4896, eabl4290, eabl5197.

Illustration: N. Fuller & C. Agosti of SayoStudio

ONLINE COVER A male Jackson's three-horned chameleon from Kenya. Capable of dynamic color changes, some of these chameleons were shipped to Oahu, Hawaii in 1972 intended for pet trade. However, the chameleons escaped and became established on the island. Whiting et al. observed that, in an environment with few lizard predators compared to Kenya, the Hawaiian chameleons evolved more striking display and anti-predator color states. The results suggest an upper threshold to signal intensity constrained by natural selection, even in species capable of dynamic color change.

ONLINE COVER Boosting Locally Buffs Up Vaccine-Induced Immunity. This month’s cover shows an immunofluorescence image of a germinal center in a mouse lymph node 5 weeks after a priming immunization with influenza hemagglutinin. Primed B cells fate-mapped for AID expression (green) are present in the central area of a follicle of IgD-expressing B cells (red) near CD21/35-expressing follicular dendritic cells (blue). Kuraoka et al. observed more fate-mapped memory B cells in lymph node germinal centers when booster immunizations were given at the same tissue site as the original immunization rather than on the opposite side.

ONLINE COVER Special Issue on Robots in the Wild. Robots have been successfully deployed in a wide range of domains–including land, sea, air, and space–for a variety of applications such as search and rescue, oceanography, wildlife surveys, and space exploration. In this issue, Zhou et al. have developed a trajectory planner for swarms of micro drones that can be implemented using only an onboard computer. Their planner computes trajectories based on limited information from the drone's onboard sensors to enable collision-free flight in cluttered environments in the wild. This month's cover is a photo illustration of a swarm of micro-drones flying through a forest (see also the Focus by Soria).

ONLINE COVER This week, Vagena et al. reveal the neural circuits by which ASB4 affects appetite and glucose homeostasis. The image shows ASB4-positive cells (red) in the mouse hypothalamus.

ONLINE COVER Helping with Healing. This image shows migrating keratinocytes in red, forming an "epithelial tongue" 5 days after skin wounding (nuclei are stained blue). Marjanovic et al. found that the tumor suppressor miR193b-3p was overexpressed in diabetic foot ulcers, leading to impaired keratinocyte migration and poor wound healing despite activation of tumor-associated pathways. Treatment with a miR193b-3p antagomiR led to improved keratinocyte migration and wound healing in mice. The overexpression of miR193b-3p may explain both the poor healing and the low incidence of cancer development in diabetic foot ulcers and suggests a potential treatment strategy for this condition.