Michelle Obama walks with Nelson Mandela’s wife Graca Machel as she visits the Nelson Mandela Foundation in Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

In this photo provided by the Nelson Mandela Foundation on Tuesday, June 21, 2011, Michelle Obama, accompanied by her daughters, Malia, left and Sasha, meet former South African President Nelson Mandela, at this home, in Houghton, South Africa.

(AP Photo/ Debbie Yazbek, Nelson Mandela Foundation)

In this photo provided by the Nelson Mandela Foundation on Tuesday, June 21, 2011, Michelle Obama, left, with former South African President Nelson Mandela, at this home, in Houghton, South Africa.

(AP Photo/ Debbie Yazbek, Nelson Mandela Foundation)

Michelle Obama stands with daughter Sasha, her mother Marian Robinson, and Graca Machel, wife of Nelson Mandela, as they listen to Verne Harris as he shows them artifacts from Nelson Mandela’s imprisonment as they visit the Nelson Mandela Foundation in Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

In this photo provided by the Nelson Mandela Foundation on Tuesday, June 21, 2011, Sello Hatang and Sahm Venter from the Nelson Mandela Foundation present Michelle Obama second right, accompanied by her daughter, Sasha, with former president Nelson Mandela’s newest book entitled ‘Nelson Mandela by Himself’, in Houghton, South Africa.

(AP Photo/ Debbie Yazbek, Nelson Mandela Foundation)

Michelle Obama walks with Nelson Mandela’s wife Graca Machel as she visits the Nelson Mandela Foundation in Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

Michelle Obama, daughters Sasha and Malia, visits the Emthonjeni Community Center in Zandspruit Township, Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

Michelle Obama, along with her mother Marian Robinson, back to camera center, daughters Malia and Sasha, second and third from left, nephew Avery Robinson, fourth from left, and niece Leslie Robinson, rear center, dance with children and caretakers as they visit the Emthonjeni Community Center in Zandspruit Township, Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

Marian Robinson, mother of first lady Michelle Obama, takes a bow after they danced with children during a visit to the Emthonjeni Community Center in Zandspruit Township, Johannesburg, South Africa, Tuesday, June 21, 2011. Pictured at rear, from left to right: Daughters Malia and Sasha; nephew Avery Robinson and niece Leslie Robinson.

(AP Photo/Charles Dharapak, Pool)

Michelle Obama meets with children during a visits the Emthonjeni Community Center in Zandspruit Township, Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

Michelle Obama dances with children as she visits the Emthonjeni Community Center in Zandspruit Township, Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

Michelle Obama, with daughters Sasha, center, and Malia, take turns reading to children from “The Cat in the Hat,” by Dr. Seuss, during their visit to the Emthonjeni Community Center in Zandspruit Township, Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

Malia Obama and Sasha Obama are embraced by children as they accompany their mother, first lady Michelle Obama on a visit to the Emthonjeni Community Center in Zandspruit Township, Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

Michelle Obama poses for a photo with young women leaders during her visit to the Apartheid Museum in Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)

Michelle Obama, along with daughters Sasha and Malia, visit the Apartheid Museum in Johannesburg, South Africa, Tuesday, June 21, 2011.

(AP Photo/Charles Dharapak, Pool)