It's often the case in science that we have a fuzzy concept of a process or pathway before the fine details come into focus. And this is certainly true for mitochondrial fusion — a process that requires the sequential joining of two sets of membranes. On page 468, Amy D. Mozdy and Janet M. Shaw describe how these coordinated fusion events rely on a GTPase called 'fuzzy onions' or Fzo, and discuss how recent studies are bringing the role of Fzo into focus. Next, on page 446, Kirsi Riento and Anne J. Ridley discuss ROCKs/Rho kinases. ROCKs were the first Rho effectors to be discovered and they can affect cell motility. However, it is now becoming clear that there are new roles for ROCKs in cytokinesis, mitosis, cell size and differentiation. And, on page 435, Stephen C. West discusses homologous recombination, and describes how our understanding of the proteins and mechanisms that drive this process has been clarified over the past few years.

It's sometimes the case, though, that we have a relatively clear view of a process or pathway and then new, fuzzy concepts emerge. For example, ubiquitin modification is well known to target proteins to the 26S proteasome for proteolysis, but now new, non-proteolytic functions for ubiquitylation — in particular, monoubiquitylation — are coming to light. In an Opinion article on page 491 Pier Paolo Di Fiore, Simona Polo and Kay Hofmann discuss how monoubiquitylation affects protein function and consider how mono- versus polyubiquitylation could be regulated.

Finally, there's an approach we can take to help us bring fuzzy ideas into focus faster — collaboration. On page 497, Valerie Daggett and Alan Fersht describe their view of the mechanism of protein folding — a detailed view that is based on nearly ten years of collaboration between a theoretician and an experimentalist.