Abstract: Disclosed is a reference standard for a detectable entity, the reference standard comprising a support medium, such as an embedding medium, a compact particle having a compact shape with a quantity of detectable entity coupled thereto and supported by the medium, in which the compact particle is a biological, such as a cellular compact particle. We also disclose a reference standard for a detectable entity, the reference standard comprising a support medium, such as an embedding medium, a compact particle having a compact shape with a quantity of detectable entity coupled thereto and supported by the medium, in which the compact particle is a non-biological compact particle, such as a non-cellular compact particle having cell-like dimensions, preferably less than 1.5 mm.