微粒体（英语：Microsome）在细胞生物学中定义为从内质网的碎片所得到的小型囊泡。必须将肝脏或其他组织磨碎 (均质化)之后，才能得到微粒体。微粒体含有细胞色素P450（CYP）酶，与氧化代谢有关。

微粒体能够在不同的离心速度之下，从其他的细胞胞器区隔出来、浓缩并分离。未破碎的细胞、细胞核与粒线体在一万g点的离心速度可以被沉淀并分离出来，而P450及其他可溶性酵素与内质网碎片，保留在溶液中 (g值代表地球的重力加速度)。在更快速的十万g值离心旋转之下，内质网会沉淀成粒状或块状，而可溶性酵素则保留在表层悬浮液中。依照这个方式，微粒体中的细胞色素P450可以被浓缩并分离。由于P450中的辅助因子，血基质，含有铁元素，微粒体呈现红褐色。P450在老鼠和人类肝脏中的含量相当豊富。 微粒体是细胞被匀浆破碎时, 内膜系统的膜结构破裂后自己重新封闭起来的小囊泡(主要是内质网和高尔基体), 这些小囊泡的直径大大100 nm左右, 是异质性的集合体, 将它们称为微粒体。 多数情况下, 微粒体是指在细胞匀浆和差速离心过程中获得的由破碎的内质网自我融合形成的近似球形的膜囊泡状结构,它包含内质网网膜和核糖体两种基本成分。在体外实验中,具有蛋白质合成、蛋白质糖基化和脂类合成等内质网的基本功能。

In cell biology, microsomes are vesicle-like artifacts re-formed from pieces of the endoplasmic reticulum (ER) when eukaryotic cells are broken-up in the laboratory; microsomes are not present in healthy, living cells.

Microsomes can be concentrated and separated from other cellular debris by differential centrifugation. Unbroken cells, nuclei, and mitochondria sediment out at 10,000 g, whereas soluble enzymes and fragmented ER, which contains cytochrome P450 (CYP), remain in solution (g is the Earth's gravitational acceleration). At 100,000 g, achieved by faster centrifuge rotation, ER sediments out of solution as a pellet but the soluble enzymes remain in the supernatant. In this way, cytochrome P450 in microsomes is concentrated and isolated. Microsomes have a reddish brown color, due to the presence of the heme. Because of the need for a multi-part protein-system, microsomes are necessary to analyze the metabolic activity of CYPs. These CYPs are highly abundant in livers of rats, mice and humans, but present in all other organs and organisms as well.