Remarkable liquid materials called colloids stiffen under impact. Researchers have studied the effect of powerful impacts such as those produced by firearms or micrometeorites. At first glance, colloids resemble homogeneous liquids such as milk or blood plasma. But in fact they consist of particles in suspension. Some colloids have remarkable properties: they may stiffen following an impact and absorb surface shocks. This property is of interest for many applications, from bulletproof vests to protective shields for satellites. Researchers found that how these colloids work can change dramatically in response to very strong impacts. The scientists have also developed a model that makes these properties easier to understand.