Spanish actress Penélope Cruz is the latest star to join Instagram, but instead of a selfie, the star's first post was dedicated to a special cause.

On Tuesday, the star shared her first post on Instagram, a short video where the 41-year-old actress introduced a little boy named Lucas to her already growing number of followers.

"Lucas is without a doubt @unoentrecienmil Not only for beating leukemia after fighting it for several years but also for how privileged he makes you feel while listening to wise words and his amazing story. Lots of love and hope in the beginning of my new adventure as director of the documentary #unoentrecienmil A documentary about children's leukemia," Cruz said in the post.

The actress then posted another photo of herself and Lucas posing together and captioned it, "My beautiful new friend Lucas. An 8 year old full of wisdom."

According to E! Online, Lucas is part of Uno Entre Cien Mil, which is a charity that works to fight child leukemia. Cruz is an ambassador for the organization.

Recently, Cruz and her husband Javier Bardem made headlines when they both appeared on stage at a U2 concert in Barcelona on Oct. 12, Billboard reported.

Bardem went up on stage at the Palau Sant Jordi arena, where the band was performing. Wearing a cowboy hat and feather boa, Bardem used the opportunity to show off some very provocative dance moves. He then proceeded to dance on various U2 members. Cruz then came on stage and pretended to be surprised by her husband's dancing dirty.

Check out the video of the surprise appearance below.