Nervous systems come in all shapes and sizes, and have evolved to match the needs of specific organisms. Non-mammalian neuroscience offers a host of preparations with interesting behaviours and neural circuitry. The reviews in this Insight sample the advantages of several of these experimental preparations in elucidating general neural principles.

New types of physical behaviour occur under unimaginably cold conditions, and modern laser-cooling technologies enable scientists to probe the quantum world of condensates. We review the latest research into ultracold matter and find that coherent matter waves as well as individual ultracold atoms and ions are extremely attractive for both theoretical and practical studies.

Malaria is a disease of poverty. Drug-resistant parasite strains, insecticide resistance in mosquitoes, environmental changes and increased population are contributing to its resurgence. But growing international awareness and funding is leading to new control efforts. This Insight describes the latest research developments, likely future progress and the practical impact that the new knowledge will have.

Heart disease is the world's leading cause of death, with smoking, fat-laden diets and sedentary lifestyles all detrimental to a healthy heart. But the heart is one of the most widely studied organs of the body, and a greater understanding of the processes involved at the molecular and genetic level is enabling us to make inroads in preventing and treating heart disease.

Diabetes is predicted to double in incidence in the next two decades, fuelled predominantly by modern lifestyles and an increasing incidence of obesity. Leading researchers discuss the spectrum of disorders that comprise diabetes, the biochemical causes of the complications that arise, and the best ways to treat and prevent this complex and potentially debilitating condition.

Limited energy resources and increasing environmental pollution are driving the development of flexible technological solutions that involve alternative means of energy supply and storage. This Insight illustrates how the search for cleaner, cheaper, smaller and more efficient energy technologies has been driven by developments in materials science and engineering.

Stem cell research has been transformed by successes achieved in culturing human embryonic stem cells, the building blocks for every tissue we comprise, and in manipulating their differentiation in vitro. The challenge is now on to bring stem cell therapies to the clinic. Here, top researchers cut through the hype and explain the fundamentals of stem cell biology as they see it today.

The transduction of environmental stimuli, such as odour, light and sound, into a cellular response is the first, crucial step in sensory processing. Many molecules involved in the different transduction pathways have been identified in the past few years. And as this Collection of reviews shows, although our senses encode a vast diversity of signals, similarities in transduction mechanisms are common.

Much of our fascination with Mars relates to the possibility that liquid water exists at or near the martian surface, and therefore that life may have taken hold or even exists there today. A series of interrelated reviews describes the evolution of this most Earth-like of the planets in our Solar System, from the differentiation and solidification of the martian core to the dynamics of its atmosphere.

Natural selection has honed the defence strategies of plants over 1.6 billion years. Besides exciting practical applications such as engineering disease resistance, a theme that emerges throughout this Insight is how molecules and mechanisms involved in plant defence have direct homologues in animals. But plant defence strategies have evolved in directions and to levels of sophistication not seen in animals.

Cancer is an umbrella term covering a plethora of conditions characterized by unscheduled and uncontrolled cellular proliferation. Almost any mammalian organ and cell type can succumb to oncogenic transformation, giving rise to a bewildering array of clinical outcomes. In this Insight, nine articles illustrate how diverse and dynamic cancer research is at the start of the 21st century.

The scale of the HIV epidemic is far greater than was predicted a decade ago. Around 36 million people are living with HIV, 20 million have already died, and 16,000 new infections occur daily. Here we examine the biology of the virus and the disease it causes, give an overview on the status of the AIDS pandemic, and review the efforts underway to control and curb it.