Abstract: We disclose a reference standard for a detectable entity, the reference standard comprising a support medium, preferably 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, preferably cellular compact particle, preferably a cellular compact particle. We also disclose a reference standard for a detectable entity, the reference standard comprising a support medium, preferably 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, preferably a non-cellular compact particle having cell-like dimensions, preferably less than 1.5 mm.