Instant messaging is evolving beyond just text, reports BBC ClickOnline North America technology correspondent Ian Hardy.
In 1996 a little known Israeli company wrote a piece of software that quickly became one of the most downloaded programs on the web and revolutionised global communications.
Instant messaging is popular at work and at home
It enabled any two people anywhere to type messages to each other in real time.
ICQ was a prototype instant messaging (IM) system that within two years had 11 million users.
It attracted the attention of internet powerhouse America Online, which bought it outright in 1998 for $287 million.
Since then scores of companies have produced similar products that can usually be obtained free of charge.
"If you live in Europe or America and you have friends or family throughout the world and you use the phone to make calls then it is pretty expensive," said Jonathan Roubini, lead analyst at PC Magazine.
"The advantage of IM is that anybody who has a computer can just go online and chat with family, friends or colleagues throughout the world."
Instant Messaging has a huge user base worldwide. AOL alone carries two billion messages every day and the IM software stays open on the desktop for an average of six hours a day.
It is little wonder that all the big players have recently announced major upgrades to their IM services.
The market is huge. Yahoo Messenger has an estimated 19 million US users, and the demographics have changed dramatically in the last couple of years.
"IM is no longer just for teenagers, early adopters or advanced technology users, it really is for everybody," said Lisa Mann of Yahoo Messenger.
"We have a very broad user base. We have people who are in school, we have senior citizens, people who use it at home, people who use it at work."
Yahoo, like all IM developers, is trying to get more customers to stick around for longer.
New offerings include integrated radio station feeds, characters that represent you whilst on line, customisable backgrounds, and 13 new emoticons.
"As our users become more and more savvy with what's going on in computers, I think they're just going to gobble this stuff up," said Barbara McNally of AOL Messenger.
"The more video you can add, the more music you can add, the more graphics you can add, the more you can make it user interactive the better off they'll be.
"IM as text is just the basis and we're adding everything on top of it."
On the go
Games that can handle multiple players in real time are also becoming a big part of the instant messaging expansion strategy.
So too are mobile devices. Microsoft, Yahoo and AOL have done deals to put smaller versions of their software on mobile phones, PDAs and even gaming devices.
Is the phone in danger of being replaced by instant messaging?
This is helped by the fact that SMS, hugely popular in Europe and elsewhere, has been slow to take off in America.
"Here in the US we are the second largest sender or receiver of messages on the mobile network," said Steven McArthur of AOL.
"Our AOL members and our customers at large have embraced IM on the mobile platform.
"We're enjoying about a 15% growth rate per month of IM traffic on the mobile network."