text: Kevin Hart is calling on his fellow celebrities to help make a difference in helping the victims of Hurricane Harvey. 
   
   The comedian posted a video to Instagram starting a new "challenge" he's hoping will sweep social media among his famous friends. He admits that he's putting aside the silliness to discuss something more serious. 
   
   "I'm starting a real challenge," he starts before adding that he will "lead the charge in stepping up this way." Hart will donate $25,000 to the American Red Cross to help those suffering from damages and injuries caused by the hurricane that has left some people in Texas homeless and thousands more without electricity. ||||| (CNN) Hurricane Harvey may have forced Coldplay to cancel its concert in Houston last week, but the city is clearly on the band's mind. 
   
   At its concert in Miami on Monday night, the band performed a song it wrote for the flooded Texas city. 
   
   "This is because we all grew up loving country music, and of course that's kind of what we think of when we go to Texas," frontman Chris Martin told the crowd at Miami's Hard Rock Stadium. 
   
   He then added: 
   
   "This is a new song and we'll never play this again. It's a one-off and it's called 'Houston.'" 
   
   Read More ||||| Not even Kevin Hart could have predicted this kind of response. 
   
   With a tropical storm continuing to devastate residents of Houston, Texas, the 38-year-old comedian launched the Hurricane Harvey Relief Challenge Monday to support relief efforts in the area. He donated $25,000 and asked Beyoncé, Dave Chappelle, Jay-Z, Dwayne Johnson, Chris Rock, Jerry Seinfeld and Justin Timberlake to match his donation. "Keep your head up Houston and keep your faith," Hart wrote Tuesday. "I love you all and my prayers are with you!" 
   
   Proceeds will benefit the American Red Cross. 
   
   Due in part to Hart, other celebrities began to share their support publicly. 
   
   Kim Kardashian announced her family's generous pledge Tuesday: ||||| Sandra Bullock is flexing her star power to aid relief efforts in the wake of Hurricane Harvey. 
   
   The A-list actress has pledged $1 million to help victims of the tropical storm that has devastated the Houston, Tex. area, E! News can confirm. Bullock's generous donation will benefit the American Red Cross in its ongoing effort to help those impacted by the catastrophic flooding and destruction along Texas' Gulf Coast. 
   
   "I'm just grateful I can do it," Bullock (who owns a home in Austin) said in a statement. "We have to take care of one another." 
   
   Bullock is the latest celebrity to pitch in with a generous financial contribution. Hours ago, Kim Kardashian and the rest of her famous family donated $500,000 to the Red Cross. Comedian Kevin Hart also launched his own Hurricane Harvey Relief Challenge, encouraging fellow stars to give $25,000 to assist Texas residents rendered homeless or without electricity amid the natural disaster.
target: – Add Sandra Bullock's name to the list of celebs helping out in the wake of Hurricane Harvey. And she's doing so in a big way: Bullock has pledged $1 million via the American Red Cross to help victims. "I'm just grateful I can do it," Bullock, who owns a home in Austin, tells E! News. Other big names stepping up include the Kardashians, who have donated $500,000, and Kevin Hart, who launched a challenge to get fellow celebs to donate $25,000. Meanwhile, Coldplay, which had to cancel a gig in Houston, wrote a song in tribute to the city, which you can hear them perform via CNN.