An apparatus that allows for separating and collecting a concentrated fraction of a fluid, such as a whole blood sample, adipose tissue, or a bone marrow sample. The apparatus, when used with a centrifuge, allows for the creation of at least three fractions in the apparatus. It also provides for a new method of extracting the buffy coat phase from a whole blood sample. The apparatus includes a container to be placed to a centrifuge after being filled with a whole blood sample. A buoy or fraction separator, which has a density less than that of red blood cells of a whole blood sample, is disposed in the container. During the centrifuge process the buoy separates the red blood cells from another fraction of the whole blood. After the centrifuge process is finished a plunger is used to produce at least two other fractions, including a plasma fraction and a buffy coat. Then, the buffy coat may be removed from the container without commingling the fractions of the sample.