Intro: I’m Tanesha Nicole and this is Ask A Scientist. Today, I’m talking with Dr. Emily Limerick from the National Heart, Lung, and Blood Institute at NIH about clinical trials. TN: Dr. Limerick, what is a clinical trial? EL: Interventional trials are where patients perhaps get a medicine, or try a new vaccine, or some intervention that they're receiving. TN: How do trials progress? EL: The earliest phases are for seeing whether that type of intervention is safe. The next phase of testing and trials is to look at how effective that medication or intervention is. The last phase is the rollout phase and how effective it is in real life use. TN: Are there laws and guidelines in place to protect participants? EL: There are so many levels of protection to make sure that patients and their safety are the priority. There's an infrastructure that helps promote safety, but it's really a decision that each individual participant can make. Outro: For more information on clinical trials, visit nhlbi.nih.gov.