In the four decades since two university computers were first linked to each other over the prototype internet, scientific researchers have been innovators, early adopters and prolific adapters of internet technologies. Electronic mail, file transfer protocol, telnet, Gopher and the World Wide Web were all developed and applied first in research communities. The Web's development for sharing of information in the high-energy physics community unexpectedly heralded the internet's extension into many aspects of commerce, community, entertainment and governance. But despite the rapid proliferation and diversification of both over the past 15 years, the internet in its various forms has scientific communication indelibly inscribed into its fabric, and internet communication is thoroughly integrated into the practice of science. This chapter reviews some effects of the internet's emergence as a principal means of professional scientific communication, and of public communication of science and technology. It notes several paradoxes that characterise these developments, for example the contradictory trends towards easier collaboration across continents, and towards greater fragmentation. It notes the very significant disturbances caused by electronic publishing in the all-important field of scientific journals. It suggests that these and other developments have made more completely porous than before the boundaries between professional and public communication, facilitating public access to previously private spaces, and thus 'turning science communication inside-out'.