As the liberation of the Nazi death camp Auschwitz is being remembered across the world, one place where this is particularly poignant is in Rwanda - a country still coming to terms with its own trauma.
By Robert Walker
BBC correspondent in Kigali
After World War II, when the full horror of the Jewish Holocaust was revealed, the world said: "Never again".
Mass graves at the memorial contain up to 250,000 people
But in 1994 an extremist Hutu government in Rwanda began the systematic slaughter of the minority Tutsis.
It is estimated some 800,000 people were killed in 100 days as the rest of the world stood by.
On a hill in the Rwandan capital Kigali a memorial stands to those killed in the genocide.
Mass graves contain anywhere up to 250,000 people and inside a specially constructed building there are displays teaching a new generation of Rwandans about what happened in 1994.
But it is not only the Rwandan genocide which is remembered here.
There are exhibitions about other mass killings during the past century, of the Namibian Herero people, the Armenians and of the Jews during the Holocaust.
Teddy Mugabo lost her grandparents and many other relatives in 1994. Like other Rwandan students visiting the memorial, she is now also learning about the Holocaust.
"It shows how the Nazis started segregating people and it shows the way they measured the nose and eyes to show that they are different people.
"In Rwanda when they were killing Tutsis they did the same thing. They measured the nose. They were measuring the eyes, heights and it is very similar."
Like the Jews during the Holocaust, Tutsis in Rwanda were systematically eliminated because of their identity.
Blaming ethnic strife
In the aftermath of both genocides, the world said: "Never again".
1994: RWANDA'S GENOCIDE
6 April: Rwandan Hutu President Habyarimana killed when plane shot down
April -July: An estimated 800,000 Tutsis and moderate Hutus killed
July: Tutsi-led rebel movement RPF captures Rwanda's capital Kigali
July: Two million Hutus flee to Zaire, now the DRC
But many Rwandans who saw UN troops stand aside in 1994 are sceptical that the world would act differently today.
Tom Ndahiro of the Rwandan Human Rights Commission says western countries are still not ready to prevent genocide in African countries - unless their national interests are at stake.
"What Nato did in former Yugoslavia was different from what it did on Darfur or in Rwanda.
"When it happens to Rwanda - [there's a] sense of saying: 'Well it's the Rwandans - savages, tribal warfare, ethnic strife.' And it's nonsense."
But the organisers of Kigali's memorial hope that by teaching new generations the painful history of the Rwandan genocide and the Holocaust the promises of "Never again" really will be kept next time.