The Princess of Wales has said "not enough is being done" to recognise the "unique potential" of early childhood.
Kate vowed to "do everything I can" to "secure much greater focus on those first crucial few years", writing in the Daily Telegraph.
The princess said people need to fully appreciate early childhood and do all they can to nurture children and those who care for them if society is to address the complex challenges it faces.
She wrote: "Over the past 10 years, talking to a wide range of experts about how we deal with societal issues like poor mental and physical health, I have become more and more sure of one thing: if we are going to create a healthier and happier society for future generations, we must start by understanding and acknowledging the unique importance of the first five years of life.
"Early childhood, from pregnancy to the age of five, fundamentally impacts our whole lives, establishing the core foundations which allow us to go on to thrive as individuals, with one another, as a community and as a society."
She said the body of evidence to support this has grown substantially over the past 30 years, adding that we now know that in the first five years of our lives our brains develop faster than at any other time and that the impact of those years is "hugely significant".
Writing for Saturday's newspaper, she said: "It is the way we develop through our experiences, relationships and interactions at that very young age that shapes everything from our ability to form relationships and succeed at work, to our mental and physical health as adults.
"There are fantastic examples of what can be achieved when we recognise the unique potential of early childhood and build a safe and loving world around a child.
"But not enough is being done. If we are going to tackle the sorts of complex challenges we face today like homelessness, violence and addiction, which are so often underpinned by poverty and poor mental health, we have to fully appreciate those most preventative years and do everything we can to nurture our children and those who care for them.
"We have an incredible opportunity, armed with all we now know as a result of the work of dedicated scientists, researchers and practitioners, to make a huge difference to the mental and physical health of generations to come.
"That is why I am determined to continue to shine a light on this issue and to do everything I can to secure much greater focus on those first crucial few years for the youngest members of our society - they are, after all, our future."
Kate has focused on mental health and the early years of childhood as she has developed her role over the years, and is known to meticulously research the issues facing the charities she works with.
She has previously visited Denmark to learn more about their investment in early childhood development, having launched The Royal Foundation Centre for Early Childhood in June 2021, which aims to raise awareness of the importance of early years experiences in shaping society over the long term.
