Title: Cell (biology)
Content: 1632–1723: Antonie van Leeuwenhoek taught himself to make lenses, constructed basic optical microscopes and drew protozoa, such as Vorticella from rain water, and bacteria from his own mouth. ; 1665: Robert Hooke discovered cells in cork, then in living plant tissue using an early compound microscope. He coined the term cell (from Latin cellula, meaning "small room" ) in his book Micrographia (1665). ; 1839: Theodor Schwann and Matthias Jakob Schleiden elucidated the principle that plants and animals are made of cells, concluding that cells are a common unit of structure and development, and thus founding the cell theory. ; 1855: Rudolf Virchow stated that new cells come from 
Title: History of botany
Content:  The cell nucleus was discovered by Robert Brown in 1831. Demonstration of the cellular composition of all organisms, with each cell possessing all the characteristics of life, is attributed to the combined efforts of botanist Matthias Schleiden and zoologist Theodor Schwann (1810–1882) in the early 19th century although Moldenhawer had already shown that plants were wholly cellular with each cell having its own wall and Julius von Sachs had shown the continuity protoplasm between cell walls. From 1870 to 1880 it became clear that cell nuclei are never formed anew but always derived from the substance of another nucleus. In 1882 Flemming observed the longitudinal splitting of chromosomes in the dividing nucleus and concluded that each daughter nucleus received half 
Title: Cell theory
Content:  With continual improvements made to microscopes over time, magnification technology advanced enough to discover cells. This discovery is largely attributed to Robert Hooke, and began the scientific study of cells, known as cell biology. When observing a piece of cork under the scope and he was able to see pores. This was shocking at the time because it was believed no one else had seen these. To further support his theory, Matthias Schleiden and Theodor Schwann both studied cells of both animal and plants. What they discovered was there were significant differences between the two types of cells. This put forth the idea that cells were not only fundamental to plants, but animals as well.
Title: Matthias Jakob Schleiden
Content:  our Knowledge of Phytogenesis (1838), in which he stated that all plants are composed of cells. Thus, Schleiden and Schwann became the first to formulate what was then an informal belief as a principle of biology equal in importance to the atomic theory of chemistry. He also recognized the importance of the cell nucleus, discovered in 1831 by the Scottish botanist Robert Brown, and sensed its connection with cell division. He became professor of botany at the University of Dorpat in 1863. He concluded that all plant parts are made of cells and that an embryonic plant organism arises from the one cell. He died in Frankfurt am Main on 23 June 1881. 
Title: Cell membrane
Content:  While Robert Hooke’s discovery of cells in 1665 led to the proposal of the Cell Theory, Hooke misled the cell membrane theory that all cells contained a hard cell wall since only plant cells could be observed at the time. Microscopists focused on the cell wall for well over 150 years until advances in microscopy were made. In the early 19th century, cells were recognized as being separate entities, unconnected, and bound by individual cell walls after it was found that plant cells could be separated. This theory extended to include animal cells to suggest a universal mechanism for cell protection and development. By the second half of the 19th century, 
Title: Cell biology
Content:  Cells were first seen in 17th century Europe with the invention of the compound microscope. In 1665, Robert Hooke termed the building block of all living organisms as "cells" (published in Micrographia) after looking at a piece of cork and observing a cell-like structure, however, the cells were dead and gave no indication to the actual overall components of a cell. A few years later, in 1674, Anton Van Leeuwenhoek was the first to analyze live cells in his examination of algae. All of this preceded the cell theory which states that all living things are made up of cells and that cells are the functional and structural unit of organisms. This was ultimately concluded by plant scientist, Matthias Schleiden and animal scientist Theodor Schwann in 1838, who viewed live cells in plant and animal tissue, respectively. 19 years later, Rudolf Virchow further contributed to the cell theory, adding that all cells come from the division of pre-existing cells. Viruses are not considered in cell biology – they lack the characteristics of a living cell, and instead are studied in the microbiology subclass of virology.
Title: History of botany
Content:  During the 19th century German scientists led the way towards a unitary theory of the structure and life-cycle of plants. Following improvements in the microscope at the end of the 18th century, Charles Mirbel (1776–1854) in 1802 published his Traité d'Anatomie et de Physiologie Végétale and Johann Moldenhawer (1766–1827) published Beyträge zur Anatomie der Pflanzen (1812) in which he describes techniques for separating cells from the middle lamella. He identified vascular and parenchymatous tissues, described vascular bundles, observed the cells in the cambium, and interpreted tree rings. He found that stomata were composed of pairs of cells, rather than a single cell with 
Title: Timeline of biology and organic chemistry
Content: ?? – Jan Baptist van Helmont performed his famous tree plant experiment in which he shows that the substance of a plant derives from water, a forerunner of the discovery of photosynthesis. ; 1628 – William Harvey published An Anatomical Exercise on the Motion of the Heart and Blood in Animals ; 1651 – William Harvey concluded that all animals, including mammals, develop from eggs, and spontaneous generation of any animal from mud or excrement was an impossibility. ; 1665 – Robert Hooke saw cells in cork using a microscope. ; In 1661, 1664 and 1665, the blood cells were discerned by Marcello Malpighi. In 1678, the red blood corpuscles was described by Jan Swammerdam of Amsterdam, a Dutch naturalist and 
Title: Plant anatomy
Content:  plant anatomy, not physiology, ought to be the sole basis for plant classification. Using a scientific basis, he established structural criteria for defining and separating plant genera. In 1830, Franz Meyen published Phytotomie, the first comprehensive review of plant anatomy. In 1838 German botanist Matthias Jakob Schleiden, published Contributions to Phytogenesis, stating, "the lower plants all consist of one cell, while the higher plants are composed of (many) individual cells" thus confirming and continuing Mirbel's work. A German-Polish botanist, Eduard Strasburger, described the mitotic process in plant cells and further demonstrated that new cell nuclei can only arise from the division of other pre-existing nuclei. His Studien 
Title: Cell theory
Content:  and existence of cells in animals or plants. This conclusion was not made until Henri Dutrochet. Besides stating “the cell is the fundamental element of organization”, Dutrochet also claimed that cells were not just a structural unit, but also a physiological unit. In 1804, Karl Rudolphi and J.H.F. Link were awarded the prize for "solving the problem of the nature of cells", meaning they were the first to prove that cells had independent cell walls by the Königliche Societät der Wissenschaft (Royal Society of Science), Göttingen. Before, it had been thought that cells shared walls and the fluid passed between them this way.

Question: who discovered that plants were made of cells?
Answer: Parashara.