An artist's impression of how part of the museum will look after the renovations.
Renovation work at the National Museums Scotland has been given a £1m boost with a grant from a charitable foundation.
The cash, from the Moffat Charitable Trust, means more than £40m has now been raised for the redevelopment of the Royal Museum building in Edinburgh.
The trust was set up in 1999 by the family of the founder of the AT Mays travel agency.
The National Museums of Scotland said it was delighted with the support.
The body's director, Dr Gordon Rintoul, said: "It is only with the help of partners like these that we can deliver this transformational project, for the benefit of the people of Scotland and beyond."
The Royal Museum building forms part of the National Museums of Scotland, which was partially closed in April for three years of restoration and redevelopment.
Jamie Moffat, chairman of The Moffat Charitable Trust, which gives out about £3m every year, said: "In line with our values, The Royal Museum project will create an environment dedicated to children, community, education and art, and as such, we are willing to throw our full support behind this ambitious redevelopment."
The grant came as the main phase of building work began on the project. It will see more objects put on display and improved access and learning facilities.
The project is jointly funded by the Heritage Lottery Fund, the Scottish Government and private sources.