In 1902 Georg Maurer was the first to publish a detailed description of 
Giemsa-stained structures in the cytosol of Plasmodium falciparum-infected 
erythrocytes, today known as Maurer's clefts. Later when clefts were seen by 
electron microscopy, the description was modified to also include these, which 
has caused disagreement over the composition of Maurer's clefts. For that 
reason, Maurer's clefts were characterized during intraerythrocytic development 
of P. falciparum by simultaneously staining cytosolic structures with antibodies 
using indirect immunofluorescence assays and with Giemsa. At least three groups 
of antigens, P. falciparum erythrocyte membrane protein 1 (PfEMP1)/ 
RIFIN/SURFIN, P. falciparum histidine-rich protein 2 (PfHRP2), and exported 
proteins 1 and 2 (Exp1 and Exp2), were detected in distinct Giemsa-stained 
structures in the cytosol of infected erythrocytes, but PfHRP2 and Exp1/Exp2 
were not found in clefts by transmission electron microscopy. Therefore, 
Maurer's clefts as defined by staining with Giemsa comprise a number of 
cytoplasmic structures and antigens not included in structures called clefts and 
seen by electron microscopy.