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• Lead as a carcinogenplugin-autotooltip__plain plugin-autotooltip_bigLead as a carcinogen
  
  It's been known for centuries that Lead (Pb) is substantially toxic for humans. Its toxic effects not only disrupt the nervous system and kidney function - in recent years it's also been classed as a dangerous carcinogen. The reasons for its 'genotoxic' effects (i.e. DNA damaging) are not known.
• Ageing of organsplugin-autotooltip__plain plugin-autotooltip_bigAgeing of organs
  
  Most human ageing studies have tended to focus on older populations - often with a high incidence of chronic diseases. The aging process in young healthy adults is still largely unknown.
  
  It was discovered in the 2020s that human organs naturally 'age'
• Auxin synthesisplugin-autotooltip__plain plugin-autotooltip_bigAuxin synthesis
  
  Auxin is an essential 'plant hormone' present in all parts of all plants. It's crucially involved in cell division, cell expansion, cell differentiation, lateral root formation, flowering, and tropic responses - i.e. movement towards light sources etc.
• DNA damage detectionplugin-autotooltip__plain plugin-autotooltip_bigDNA damage detection
  
  It's estimated that the DNA of a mammalian cell is severely damaged several thousand times per day. In order to preserve the integrity of the genome, cells need to be able to accurately and rapidly detect when damage has occurred. How this is achieved is currently unknown.
• Polymer crystallizationplugin-autotooltip__plain plugin-autotooltip_bigPolymer crystallization
  
  It's been known since the 1930s that polymers (plastics etc) are not entirely random amorphous molecular chains as was once thought. In ordinary plastics for example, between 10 and 80% of the structure is 'crystalline' - or, in other words, atomically arranged in large-scale regular repeating patterns.
• The Economic Lot Scheduling Problem (ELSP)plugin-autotooltip__plain plugin-autotooltip_bigThe Economic Lot Scheduling Problem (ELSP)
  
  The Economic Lot Scheduling Problem (ELSP) was first described (and named) in 1958 by professor Jack D. Rogers at the University of California, Berkeley, US.(ref.)
  
  It's an important everyday practical issue for almost any manufacturing company involved in planning what to manufacture, when to manufacture it, and how much to manufacture.
• Multifocal motor neuropathyplugin-autotooltip__plain plugin-autotooltip_bigMultifocal motor neuropathy
  
  "Multifocal motor neuropathy (MMN) was distinguished from other motor neuropathies in 1986 and has since become a well defined condition due to its distinctive clinical presentation and response to treatment, as well as its characteristic laboratory and electrophysiologic features. It is characterized by slowly progressive, predominantly distal, asymmetric limb weakness and wasting, predominantly in the arms, as well as muscle cramps and fasciculations within an ana…
• Insect flight evolutionplugin-autotooltip__plain plugin-autotooltip_bigInsect flight evolution
  
  "Sometime in the Carboniferous Period, some 350 to 400 million years ago, when there were only two major land masses, insects began flying. How and why insect wings developed is not well understood, largely due to the scarcity of appropriate fossils from the period of their development in the Lower Carboniferous."
• Hand and digits evolutionplugin-autotooltip__plain plugin-autotooltip_bigHand and digits evolution
  
  "How the hand and digits originated from fish fins during the Devonian fin-to-limb transition remains unsolved. Controversy in this conundrum stems from the scarcity of ontogenetic data from extant lobe-finned fishes."
  
  Source :
• Human Evolutionplugin-autotooltip__plain plugin-autotooltip_bigHuman Evolution
  
  "[...] over the past 15 years, almost every part of our story, every assumption about who our ancestors were and where we came from, has been called into question. The new insights have some unsettling implications for how long we have walked the earth, and even who we really are.
• Flowering plants evolutionplugin-autotooltip__plain plugin-autotooltip_bigFlowering plants evolution
  
  The evolutionary pathways that produced the flowering plants (the Angiosperms) have been studied for at least 140 years.
  
  The flowering plants appear very suddenly (geologically speaking) in the fossil record, at around 100 million years ago. Before that, all known plants were
• Feather evolutionplugin-autotooltip__plain plugin-autotooltip_bigFeather evolution
  
  It has been known since the mid 1800s that many species of dinosaur had 'feathers'. Until the 1970s, it was widely assumed that the evolution of feathers happened concurrently as animals became able to 'glide' or fly.
  
  In the 1970s, fossils of several species of
• Avian flight evolutionplugin-autotooltip__plain plugin-autotooltip_bigAvian flight evolution
  
  It's now widely agreed that modern-day birds evolved, during the Mesozoic Era, from dinosaur species which survived the Cretaceous / Tertiary extinction event. (See: Avian K-T survival )
  
  But the question of how and why birds acquired the ability to fly is still being debated.
• Cell sizeplugin-autotooltip__plain plugin-autotooltip_bigCell size
  
  A detailed explanation of the factors which regulate cell size (i.e. the size to which cells grow) has not yet been found. Since (most) cells stop growing when they reach a specific size, it's suggested that there must be some feedback mechanism to restrict growth beyond that point.
• The Nuclear Matrixplugin-autotooltip__plain plugin-autotooltip_bigThe Nuclear Matrix
  
  First described in 1948, the Nuclear Matrix refers to a network of fibres found inside the nucleus of all animal, plant, fungi and bacterial (etc.) cells, It has also been termed the “Nuclear-Scaffold” or "NuMat".
  
  The function of the matrix is disputed. Some theorists suggest that it's an active structure involved in biochemical and genetic transport - as it contains proteins, chaperones, DNA/RNA-binding proteins, chromatin remodeling and transcription factors (Source :

• Auxin synthesisplugin-autotooltip__plain plugin-autotooltip_bigAuxin synthesis
  
  Auxin is an essential 'plant hormone' present in all parts of all plants. It's crucially involved in cell division, cell expansion, cell differentiation, lateral root formation, flowering, and tropic responses - i.e. movement towards light sources etc.
• Telomere lengths (ageing & disease)plugin-autotooltip__plain plugin-autotooltip_bigTelomere lengths (ageing & disease)
  
  Telomeres are often described as the 'end caps' of chromosomal DNA. They protect the terminal sections of chromosomes from progressive degradation during cell division. Uncapped, the chromosomes would not be able to repeatedly copy their end-regions without errors (due to the so-called
• Ageing of organsplugin-autotooltip__plain plugin-autotooltip_bigAgeing of organs
  
  Most human ageing studies have tended to focus on older populations - often with a high incidence of chronic diseases. The aging process in young healthy adults is still largely unknown.
  
  It was discovered in the 2020s that human organs naturally 'age'
• Cell deathplugin-autotooltip__plain plugin-autotooltip_bigCell death
  
  "Why living organisms inevitably die and what death even means in terms of physics and dynamical systems are still open questions despite the vast advances in molecular biology. Revealing how some cells die — not through biochemical processes but physics — would help to answer them."
• Persistent luminescenceplugin-autotooltip__plain plugin-autotooltip_bigPersistent luminescence
  
  functionality_unexplained
  
  Persistent luminescence (a.k.a phosphorescence, afterglow, or Long Lasting Phosphorescence (LLP)) is the name given to the phenomenon found in materials which glow in the dark after the end of an excitation with UV or visible light - mainly phosphors such as silver-activated zinc sulphide or doped strontium aluminate. They typically glow a pale green to greenish-blue colour. They are routinely used in toys, watch dials, luminous paints, safet…
• Relaxorsplugin-autotooltip__plain plugin-autotooltip_bigRelaxors
  
  functionality_unexplained
  
  Relaxors is the name given to a group of ferroelectric materials which strongly change their shape in electric fields.
  
  Examples include : lead magnesium niobate, lead magnesium niobate-lead titanate, lead lanthanum zirconate titanate, and lead scandium niobate. There are also examples based on barium.
• Covid-19plugin-autotooltip__plain plugin-autotooltip_bigCovid-19
  
  Editor's note : Because of the intense, ongoing, global research efforts related to Covid-19, it's difficult to get an accurate picture of the unknown factors. Here are some of the many as-yet-unanswered questions Why does the virus have much more serious effects in older people?
• Multifocal motor neuropathyplugin-autotooltip__plain plugin-autotooltip_bigMultifocal motor neuropathy
  
  "Multifocal motor neuropathy (MMN) was distinguished from other motor neuropathies in 1986 and has since become a well defined condition due to its distinctive clinical presentation and response to treatment, as well as its characteristic laboratory and electrophysiologic features. It is characterized by slowly progressive, predominantly distal, asymmetric limb weakness and wasting, predominantly in the arms, as well as muscle cramps and fasciculations within an ana…
• Polymer crystallizationplugin-autotooltip__plain plugin-autotooltip_bigPolymer crystallization
  
  It's been known since the 1930s that polymers (plastics etc) are not entirely random amorphous molecular chains as was once thought. In ordinary plastics for example, between 10 and 80% of the structure is 'crystalline' - or, in other words, atomically arranged in large-scale regular repeating patterns.
• DNA damage detectionplugin-autotooltip__plain plugin-autotooltip_bigDNA damage detection
  
  It's estimated that the DNA of a mammalian cell is severely damaged several thousand times per day. In order to preserve the integrity of the genome, cells need to be able to accurately and rapidly detect when damage has occurred. How this is achieved is currently unknown.
• The Economic Lot Scheduling Problem (ELSP)plugin-autotooltip__plain plugin-autotooltip_bigThe Economic Lot Scheduling Problem (ELSP)
  
  The Economic Lot Scheduling Problem (ELSP) was first described (and named) in 1958 by professor Jack D. Rogers at the University of California, Berkeley, US.(ref.)
  
  It's an important everyday practical issue for almost any manufacturing company involved in planning what to manufacture, when to manufacture it, and how much to manufacture.
• The Beeswax wreckplugin-autotooltip__plain plugin-autotooltip_bigThe Beeswax wreck
  
  The beeswax wreck is an as-yet-undiscovered shipwreck which is believed to be located somewhere off the coast of the U.S. state of Oregon, near the mouth of the Nehalem River in Tillamook County. The ship, thought to be a Spanish Manila galleon that was wrecked in the late 1600s, was evidently carrying a large cargo of beeswax, lumps of which have been found scattered along Oregon's north coast for at least two centuries.
• 'Borg' DNAplugin-autotooltip__plain plugin-autotooltip_big'Borg' DNA
  
  'Borgs' are newly discovered (2021) large functional DNA sequences found in the cell nucleus, but outside the chromosomes.
  
  They have been found, in abundance, in some species of the micro-organisms Archaea - in particular, ones which can oxidise and remove methane from the environment. On a global scale, the activities of these organisms are crucial for controlling methane levels (methane being a naturally occurring and powerful 'Greenhouse Gas').
• Nematocytes mechanismsplugin-autotooltip__plain plugin-autotooltip_bigNematocytes mechanisms
  
  Nematocytes (a.k.a nematocysts, cnidocysts or cnidae) are the stinging cells found in jellyfish, hydra, sea anemones &etc.
  
  "Though an enormous amount of work has been done on nematocysts, the problem of how they are discharged remains unsolved. There are really two separate problems. First, what is the natural stimulus which excites the cnidoblast; second, what is the physical mechanism by which the nematocyst itself discharges? There is more work on the mechanics of di…
• Cushing's diseaseplugin-autotooltip__plain plugin-autotooltip_bigCushing's disease
  
  Cushing's disease, (a.k.a Cushing's syndrome and hypercortisolism ) is a rare, life-threatening, hormonal imbalance disorder.
  
  "Cushing's syndrome, also called hypercortisolism, is a rare endocrine disorder caused by chronic exposure of the body's tissues to excess levels of cortisol - a hormone naturally produced by the adrenal gland. Exposure to too much cortisol can occur from long-term use of synthetic glucocorticoid hormones to treat inflammatory illnesses. Pituitary ade…