There were fears about the future of the Millport Marine Biological Research Station when its then owners announced in 2012 they were withdrawing funding for it.
But the environmental education charity Field Studies Council (FSC) Scotland has taken over the centre, on the Isle of Cumbrae, and will now manage it along with its existing centre in Perthshire.
The centre - which is now known as FSC Millport - is expected to undergo a programme of development and refurbishment, over the next five years, with the aim of re-establishing it as the UK's leading marine teaching location.
It comes after it secured £1.5 million of funding from North Ayrshire Council as well as £1 million of Scottish Government cash, with further resources coming from charitable trusts, academic organisations and private donations.
Education Secretary Mike Russell visited the centre, where he said he was "delighted" to meet staff and students "in such positive circumstances".
He added: "Since the announcement of the closure in 2012, all of the partners - the Field Studies Council, North Ayrshire Council, Highlands and Islands Enterprise and the Scottish Funding Council - have worked tirelessly with us to ensure that this invaluable educational and research facility was not lost.
"Generations of school and university students have been taught at this facility and it is heartening that this excellent work will continue so that many more people can experience the residential classes and unique outdoor activities provided here."
Robert Lucas, FSC chief executive officer, said: "The investment in Millport ensures a new and sustainable future for the centre, building on its international reputation for marine science field teaching. We will be using all of our experience to provide exciting outdoor learning opportunities for people of all ages. The centre is also ideally located to act as a base for research on the Clyde Basin, and later this year will be hosting a research seminar.
"Today marks an important step for FSC in cementing our commitment to research and education in Scotland and maximising passion and understanding of the biodiversity and landscape."