A vital part of modern science. Practitioners have always understood the benefits of others checking and reviewing their work; looking for flaws and errors they may have missed. A whole industry has grown up with published journals for a myriad of eclectic subjects all publishing scientific studies and papers that have been reviewed by peers. Though necessary, the system is not without its critics.
There are people who state that some subjects can be too insular and that the emphasis is on on publication of new positve results only, failing to promote negative or replicated studies. There is also the massaging of data or methodology to try to promote certain outcomes. Peer review is designed to spot these issues, but sometimes the process can lack the tools to do so. This is why there is a such a big push for transparency in scientific testing.
(Cartoon courtesy of www.lab-initio.com/)